f3s: Kubernetes with FreeBSD - Part 6: Storage

Published at 2025-07-13T16:44:29+03:00, last updated: 08.08.2025

This is the sixth blog post about the f3s series for self-hosting demands in a home lab. f3s? The "f" stands for FreeBSD, and the "3s" stands for k3s, the Kubernetes distribution used on FreeBSD-based physical machines.

2024-11-17 f3s: Kubernetes with FreeBSD - Part 1: Setting the stage

2024-12-03 f3s: Kubernetes with FreeBSD - Part 2: Hardware and base installation

2025-02-01 f3s: Kubernetes with FreeBSD - Part 3: Protecting from power cuts

2025-04-05 f3s: Kubernetes with FreeBSD - Part 4: Rocky Linux Bhyve VMs

2025-05-11 f3s: Kubernetes with FreeBSD - Part 5: WireGuard mesh network

2025-07-14 f3s: Kubernetes with FreeBSD - Part 6: Storage (You are currently reading this)

2025-10-02 f3s: Kubernetes with FreeBSD - Part 7: k3s and first pod deployments

2025-12-07 f3s: Kubernetes with FreeBSD - Part 8: Observability

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⇢ f3s: Kubernetes with FreeBSD - Part 6: Storage
⇢ ⇢ Introduction
⇢ ⇢ Additional storage capacity
⇢ ⇢ ZFS encryption keys
⇢ ⇢ ⇢ UFS on USB keys
⇢ ⇢ ⇢ Generating encryption keys
⇢ ⇢ ⇢ Configuring `zdata` ZFS pool encryption
⇢ ⇢ ⇢ Migrating Bhyve VMs to an encrypted `bhyve` ZFS volume
⇢ ⇢ ZFS Replication with `zrepl`
⇢ ⇢ ⇢ Understanding Replication Requirements
⇢ ⇢ ⇢ Installing `zrepl`
⇢ ⇢ ⇢ Configuring `zrepl` on `f1` (sink)
⇢ ⇢ ⇢ Enabling and starting `zrepl` services
⇢ ⇢ ⇢ Monitoring replication
⇢ ⇢ ⇢ Verifying replication after reboot
⇢ ⇢ ⇢ Understanding Failover Limitations and Design Decisions
⇢ ⇢ ⇢ Mounting the NFS datasets
⇢ ⇢ Troubleshooting: Files not appearing in replication
⇢ ⇢ ⇢ Configuring automatic key loading on boot
⇢ ⇢ ⇢ Troubleshooting: zrepl Replication Not Working
⇢ ⇢ ⇢ Check if zrepl Services are Running
⇢ ⇢ ⇢ Check zrepl Status for Errors
⇢ ⇢ ⇢ Fixing "No Common Snapshot" Errors
⇢ ⇢ ⇢ Network Connectivity Issues
⇢ ⇢ ⇢ Encryption Key Issues
⇢ ⇢ ⇢ Monitoring Ongoing Replication
⇢ ⇢ CARP (Common Address Redundancy Protocol)
⇢ ⇢ ⇢ How CARP Works
⇢ ⇢ ⇢ Configuring CARP
⇢ ⇢ ⇢ CARP State Change Notifications
⇢ ⇢ NFS Server Configuration
⇢ ⇢ ⇢ Setting up NFS on `f0` (Primary)
⇢ ⇢ ⇢ Configuring Stunnel for NFS Encryption with CARP Failover
⇢ ⇢ ⇢ Creating a Certificate Authority for Client Authentication
⇢ ⇢ ⇢ Install and Configure Stunnel on `f0`
⇢ ⇢ ⇢ Setting up NFS on `f1` (Standby)
⇢ ⇢ ⇢ CARP Control Script for Clean Failover
⇢ ⇢ ⇢ CARP Management Script
⇢ ⇢ ⇢ Automatic Failback After Reboot
⇢ ⇢ Client Configuration for NFS via Stunnel
⇢ ⇢ ⇢ Configuring Rocky Linux Clients (`r0`, `r1`, `r2`)
⇢ ⇢ ⇢ NFSv4 user mapping config on Rocky
⇢ ⇢ ⇢ Testing NFS Mount with Stunnel
⇢ ⇢ ⇢ Testing CARP Failover with mounted clients and stale file handles:
⇢ ⇢ ⇢ Complete Failover Test
⇢ ⇢ Conclusion
⇢ ⇢ Future Storage Explorations
⇢ ⇢ ⇢ MinIO for S3-Compatible Object Storage
⇢ ⇢ ⇢ MooseFS for Distributed High Availability

Introduction

In the previous posts, we set up a WireGuard mesh network. In the future, we will also setting up a Kubernetes cluster. Kubernetes workloads often require persistent storage for databases, configuration files, and application data. Local storage on each node has significant limitations:

No data sharing: Pods (once we run Kubernetes) on different nodes can't access the same data
Pod mobility: If a pod moves to another node, it loses access to its data
No redundancy: Hardware failure means data loss

This post implements a robust storage solution using:

CARP: For high availability with automatic IP failover
NFS over stunnel: For secure, encrypted network storage
ZFS: For data integrity, encryption, and efficient snapshots
`zrepl`: For continuous ZFS replication between nodes

The result is a highly available, encrypted storage system that survives node failures while providing shared storage to all Kubernetes pods.

Other than what was mentioned in the first post of this blog series, we aren't using HAST, but `zrepl` for data replication. Read more about it later in this blog post.

Additional storage capacity

We add 1 TB of additional storage to each of the nodes (`f0`, `f1`, `f2`) in the form of an SSD drive. The Beelink mini PCs have enough space in the chassis for the extra space.

Upgrading the storage was as easy as unscrewing, plugging the drive in, and then screwing it back together again. The procedure was uneventful! We're using two different SSD models (Samsung 870 EVO and Crucial BX500) to avoid simultaneous failures from the same manufacturing batch.

We then create the `zdata` ZFS pool on all three nodes:

paul@f0:~ % doas zpool create -m /data zdata /dev/ada1
paul@f0:~ % zpool list
NAME    SIZE  ALLOC   FREE  CKPOINT  EXPANDSZ   FRAG    CAP  DEDUP    HEALTH  ALTROOT
zdata   928G  12.1M   928G        -         -     0%     0%  1.00x    ONLINE  -
zroot   472G  29.0G   443G        -         -     0%     6%  1.00x    ONLINE  -

paul@f0:/ % doas camcontrol devlist
<512GB SSD D910R170>               at scbus0 target 0 lun 0 (pass0,ada0)
  at scbus1 target 0 lun 0 (pass1,ada1)
paul@f0:/ %

To verify that we have a different SSD on the second node (the third node has the same drive as the first):

paul@f1:/ % doas camcontrol devlist
<512GB SSD D910R170>               at scbus0 target 0 lun 0 (pass0,ada0)
          at scbus1 target 0 lun 0 (pass1,ada1)

ZFS encryption keys

ZFS native encryption requires encryption keys to unlock datasets. We need a secure method to store these keys that balances security with operational needs:

Security: Keys must not be stored on the same disks they encrypt
Availability: Keys must be available at boot for automatic mounting
Portability: Keys should be easily moved between systems for recovery

Using USB flash drives as hardware key storage provides a convenient and elegant solution. The encrypted data is unreadable without physical access to the USB key, protecting against disk theft or improper disposal. In production environments, you may use enterprise key management systems; however, for a home lab, USB keys offer good security with minimal complexity.

UFS on USB keys

We'll format the USB drives with UFS (Unix File System) rather than ZFS for simplicity. There is no need to use ZFS.

Let's see the USB keys:

USB keys

To verify that the USB key (flash disk) is there:

paul@f0:/ % doas camcontrol devlist
<512GB SSD D910R170>               at scbus0 target 0 lun 0 (pass0,ada0)
  at scbus1 target 0 lun 0 (pass1,ada1)
          at scbus2 target 0 lun 0 (da0,pass2)
paul@f0:/ %

Let's create the UFS file system and mount it (done on all three nodes `f0`, `f1` and `f2`):

paul@f0:/ % doas newfs /dev/da0
/dev/da0: 15000.0MB (30720000 sectors) block size 32768, fragment size 4096
        using 24 cylinder groups of 625.22MB, 20007 blks, 80128 inodes.
        with soft updates
super-block backups (for fsck_ffs -b #) at:
 192, 1280640, 2561088, 3841536, 5121984, 6402432, 7682880, 8963328, 10243776,
11524224, 12804672, 14085120, 15365568, 16646016, 17926464, 19206912,k 20487360,
...

paul@f0:/ % echo '/dev/da0 /keys ufs rw 0 2' | doas tee -a /etc/fstab
/dev/da0 /keys ufs rw 0 2
paul@f0:/ % doas mkdir /keys
paul@f0:/ % doas mount /keys
paul@f0:/ % df | grep keys
/dev/da0             14877596       8  13687384     0%    /keys

USB keys stuck in

Generating encryption keys

The following keys will later be used to encrypt the ZFS file systems. They will be stored on all three nodes, serving as a backup in case one of the keys is lost or corrupted. When we later replicate encrypted ZFS volumes from one node to another, the keys must also be available on the destination node.

paul@f0:/keys % doas openssl rand -out /keys/f0.lan.buetow.org:bhyve.key 32
paul@f0:/keys % doas openssl rand -out /keys/f1.lan.buetow.org:bhyve.key 32
paul@f0:/keys % doas openssl rand -out /keys/f2.lan.buetow.org:bhyve.key 32
paul@f0:/keys % doas openssl rand -out /keys/f0.lan.buetow.org:zdata.key 32
paul@f0:/keys % doas openssl rand -out /keys/f1.lan.buetow.org:zdata.key 32
paul@f0:/keys % doas openssl rand -out /keys/f2.lan.buetow.org:zdata.key 32
paul@f0:/keys % doas chown root *
paul@f0:/keys % doas chmod 400 *

paul@f0:/keys % ls -l
total 20
*r--------  1 root wheel 32 May 25 13:07 f0.lan.buetow.org:bhyve.key
*r--------  1 root wheel 32 May 25 13:07 f1.lan.buetow.org:bhyve.key
*r--------  1 root wheel 32 May 25 13:07 f2.lan.buetow.org:bhyve.key
*r--------  1 root wheel 32 May 25 13:07 f0.lan.buetow.org:zdata.key
*r--------  1 root wheel 32 May 25 13:07 f1.lan.buetow.org:zdata.key
*r--------  1 root wheel 32 May 25 13:07 f2.lan.buetow.org:zdata.key

After creation, these are copied to the other two nodes, `f1` and `f2`, into the `/keys` partition (I won't provide the commands here; create a tarball, copy it over, and extract it on the destination nodes).

Configuring `zdata` ZFS pool encryption

Let's encrypt our `zdata` ZFS pool. We are not encrypting the whole pool, but everything within the `zdata/enc` data set:

paul@f0:/keys % doas zfs create -o encryption=on -o keyformat=raw -o \
  keylocation=file:///keys/`hostname`:zdata.key zdata/enc
paul@f0:/ % zfs list | grep zdata
zdata                                          836K   899G    96K  /data
zdata/enc                                      200K   899G   200K  /data/enc

paul@f0:/keys % zfs get all zdata/enc | grep -E -i '(encryption|key)'
zdata/enc  encryption            aes-256-gcm                               -
zdata/enc  keylocation           file:///keys/f0.lan.buetow.org:zdata.key  local
zdata/enc  keyformat             raw                                       -
zdata/enc  encryptionroot        zdata/enc                                 -
zdata/enc  keystatus             available                                 -

All future data sets within `zdata/enc` will inherit the same encryption key.

Migrating Bhyve VMs to an encrypted `bhyve` ZFS volume

We set up Bhyve VMs in a previous blog post. Their ZFS data sets rely on `zroot`, which is the default ZFS pool on the internal 512GB NVME drive. They aren't encrypted yet, so we encrypt the VM data sets as well now. To do so, we first shut down the VMs on all three nodes:

paul@f0:/keys % doas vm stop rocky
Sending ACPI shutdown to rocky

paul@f0:/keys % doas vm list
NAME     DATASTORE  LOADER     CPU  MEMORY  VNC  AUTO     STATE
rocky    default    uefi       4    14G     -    Yes [1]  Stopped

After this, we rename the unencrypted data set to `_old`, create a new encrypted data set, and also snapshot it as `@hamburger`.

paul@f0:/keys % doas zfs rename zroot/bhyve zroot/bhyve_old
paul@f0:/keys % doas zfs set mountpoint=/mnt zroot/bhyve_old
paul@f0:/keys % doas zfs snapshot zroot/bhyve_old/rocky@hamburger

paul@f0:/keys % doas zfs create -o encryption=on -o keyformat=raw -o \
  keylocation=file:///keys/`hostname`:bhyve.key zroot/bhyve
paul@f0:/keys % doas zfs set mountpoint=/zroot/bhyve zroot/bhyve
paul@f0:/keys % doas zfs set mountpoint=/zroot/bhyve/rocky zroot/bhyve/rocky

Once done, we import the snapshot into the encrypted dataset and also copy some other metadata files from `vm-bhyve` back over.

paul@f0:/keys % doas zfs send zroot/bhyve_old/rocky@hamburger | \
  doas zfs recv zroot/bhyve/rocky
paul@f0:/keys % doas cp -Rp /mnt/.config /zroot/bhyve/
paul@f0:/keys % doas cp -Rp /mnt/.img /zroot/bhyve/
paul@f0:/keys % doas cp -Rp /mnt/.templates /zroot/bhyve/
paul@f0:/keys % doas cp -Rp /mnt/.iso /zroot/bhyve/

We also have to make encrypted ZFS data sets mount automatically on boot:

paul@f0:/keys % doas sysrc zfskeys_enable=YES
zfskeys_enable:  -> YES
paul@f0:/keys % doas vm init
paul@f0:/keys % doas reboot
.
.
.
paul@f0:~ % doas vm list
paul@f0:~ % doas vm list
NAME     DATASTORE  LOADER     CPU  MEMORY  VNC           AUTO     STATE
rocky    default    uefi       4    14G     0.0.0.0:5900  Yes [1]  Running (2265)

As you can see, the VM is running. This means the encrypted `zroot/bhyve` was mounted successfully after the reboot! Now we can destroy the old, unencrypted, and now unused bhyve dataset:

paul@f0:~ % doas zfs destroy -R zroot/bhyve_old

To verify once again that `zroot/bhyve` and `zroot/bhyve/rocky` are now both encrypted, we run:

paul@f0:~ % zfs get all zroot/bhyve | grep -E '(encryption|key)'
zroot/bhyve  encryption            aes-256-gcm                               -
zroot/bhyve  keylocation           file:///keys/f0.lan.buetow.org:bhyve.key  local
zroot/bhyve  keyformat             raw                                       -
zroot/bhyve  encryptionroot        zroot/bhyve                               -
zroot/bhyve  keystatus             available                                 -

paul@f0:~ % zfs get all zroot/bhyve/rocky | grep -E '(encryption|key)'
zroot/bhyve/rocky  encryption            aes-256-gcm            -
zroot/bhyve/rocky  keylocation           none                   default
zroot/bhyve/rocky  keyformat             raw                    -
zroot/bhyve/rocky  encryptionroot        zroot/bhyve            -
zroot/bhyve/rocky  keystatus             available              -

ZFS Replication with `zrepl`

Data replication is the cornerstone of high availability. While CARP handles IP failover (see later in this post), we need continuous data replication to ensure the backup server has current data when it becomes active. Without replication, failover would result in data loss or require shared storage (like iSCSI), which introduces a single point of failure.

Understanding Replication Requirements

Our storage system has different replication needs:

NFS data (`/data/nfs/k3svolumes`): Soon, it will contain active Kubernetes persistent volumes. Needs frequent replication (every minute) to minimise data loss during failover.
VM data (`/zroot/bhyve/fedora`): Contains VM images that change less frequently. Can tolerate longer replication intervals (every 10 minutes).

The 1-minute replication window is perfectly acceptable for my personal use cases. This isn't a high-frequency trading system or a real-time database—it's storage for personal projects, development work, and home lab experiments. Losing at most 1 minute of work in a disaster scenario is a reasonable trade-off for the reliability and simplicity of snapshot-based replication. Additionally, in the case of a "1 minute of data loss," I would likely still have the data available on the client side.

Why use `zrepl` instead of HAST? While HAST (Highly Available Storage) is FreeBSD's native solution for high-availability storage and supports synchronous replication—thus eliminating the mentioned 1-minute window—I've chosen `zrepl` for several important reasons:

HAST can cause ZFS corruption: HAST operates at the block level and doesn't understand ZFS's transactional semantics. During failover, in-flight transactions can lead to corrupted zpools. I've experienced this firsthand (I am confident I have configured something wrong) - the automatic failover would trigger while ZFS was still writing, resulting in an unmountable pool.
ZFS-aware replication: `zrepl` understands ZFS datasets and snapshots. It replicates at the dataset level, ensuring each snapshot is a consistent point-in-time copy. This is fundamentally safer than block-level replication.
Snapshot history: With `zrepl`, you get multiple recovery points (every minute for NFS data in our setup). If corruption occurs, you can roll back to any previous snapshot. HAST only gives you the current state.
Easier recovery: When something goes wrong with `zrepl`, you still have intact snapshots on both sides. With HAST, a corrupted primary often means a corrupted secondary as well.

FreeBSD HAST

Installing `zrepl`

First, install `zrepl` on both hosts involved (we will replicate data from `f0` to `f1`):

paul@f0:~ % doas pkg install -y zrepl

Then, we verify the pools and datasets on both hosts:

# On f0
paul@f0:~ % doas zpool list
NAME    SIZE  ALLOC   FREE  CKPOINT  EXPANDSZ   FRAG    CAP  DEDUP    HEALTH  ALTROOT
zdata   928G  1.03M   928G        -         -     0%     0%  1.00x    ONLINE  -
zroot   472G  26.7G   445G        -         -     0%     5%  1.00x    ONLINE  -

paul@f0:~ % doas zfs list -r zdata/enc
NAME        USED  AVAIL  REFER  MOUNTPOINT
zdata/enc   200K   899G   200K  /data/enc

# On f1
paul@f1:~ % doas zpool list
NAME    SIZE  ALLOC   FREE  CKPOINT  EXPANDSZ   FRAG    CAP  DEDUP    HEALTH  ALTROOT
zdata   928G   956K   928G        -         -     0%     0%  1.00x    ONLINE  -
zroot   472G  11.7G   460G        -         -     0%     2%  1.00x    ONLINE  -

paul@f1:~ % doas zfs list -r zdata/enc
NAME        USED  AVAIL  REFER  MOUNTPOINT
zdata/enc   200K   899G   200K  /data/enc

Since we have a WireGuard tunnel between `f0` and f1, we'll use TCP transport over the secure tunnel instead of SSH. First, check the WireGuard IP addresses:

# Check WireGuard interface IPs
paul@f0:~ % ifconfig wg0 | grep inet
	inet 192.168.2.130 netmask 0xffffff00

paul@f1:~ % ifconfig wg0 | grep inet
	inet 192.168.2.131 netmask 0xffffff00

Let's create a dedicated dataset for NFS data that will be replicated:

# Create the nfsdata dataset that will hold all data exposed via NFS
paul@f0:~ % doas zfs create zdata/enc/nfsdata

Afterwards, we create the `zrepl` configuration on `f0`:

paul@f0:~ % doas tee /usr/local/etc/zrepl/zrepl.yml <<'EOF'
global:
  logging:
    - type: stdout
      level: info
      format: human

jobs:
  - name: f0_to_f1_nfsdata
    type: push
    connect:
      type: tcp
      address: "192.168.2.131:8888"
    filesystems:
      "zdata/enc/nfsdata": true
    send:
      encrypted: true
    snapshotting:
      type: periodic
      prefix: zrepl_
      interval: 1m
    pruning:
      keep_sender:
        - type: last_n
          count: 10
        - type: grid
          grid: 4x7d | 6x30d
          regex: "^zrepl_.*"
      keep_receiver:
        - type: last_n
          count: 10
        - type: grid
          grid: 4x7d | 6x30d
          regex: "^zrepl_.*"

  - name: f0_to_f1_fedora
    type: push
    connect:
      type: tcp
      address: "192.168.2.131:8888"
    filesystems:
      "zroot/bhyve/fedora": true
    send:
      encrypted: true
    snapshotting:
      type: periodic
      prefix: zrepl_
      interval: 10m
    pruning:
      keep_sender:
        - type: last_n
          count: 10
        - type: grid
          grid: 4x7d
          regex: "^zrepl_.*"
      keep_receiver:
        - type: last_n
          count: 10
        - type: grid
          grid: 4x7d
          regex: "^zrepl_.*"
EOF

We're using two separate replication jobs with different intervals:

`f0_to_f1_nfsdata`: Replicates NFS data every minute for faster failover recovery
`f0_to_f1_fedora`: Replicates Fedora VM every ten minutes (less critical)

The Fedora VM is only used for development purposes, so it doesn't require as frequent replication as the NFS data. It's off-topic to this blog series, but it showcases, hows `zrepl`'s flexibility in handling different datasets with varying replication needs.

Furthermore:

We're specifically replicating `zdata/enc/nfsdata` instead of the entire `zdata/enc` dataset. This dedicated dataset will contain all the data we later want to expose via NFS, keeping a clear separation between replicated NFS data and other local encrypted data.
The `send: encrypted: false` option turns off ZFS native encryption for the replication stream. Since we're using a WireGuard tunnel between `f0` and `f1`, the data is already encrypted in transit. Disabling ZFS stream encryption reduces CPU overhead and improves replication performance.

Configuring `zrepl` on `f1` (sink)

On `f1` (the sink, meaning it's the node receiving the replication data), we configure `zrepl` to receive the data as follows:

# First, create a dedicated sink dataset
paul@f1:~ % doas zfs create zdata/sink

paul@f1:~ % doas tee /usr/local/etc/zrepl/zrepl.yml <<'EOF'
global:
  logging:
    - type: stdout
      level: info
      format: human

jobs:
  - name: sink
    type: sink
    serve:
      type: tcp
      listen: "192.168.2.131:8888"
      clients:
        "192.168.2.130": "f0"
    recv:
      placeholder:
        encryption: inherit
    root_fs: "zdata/sink"
EOF

Enabling and starting `zrepl` services

We then enable and start `zrepl` on both hosts via:

# On f0
paul@f0:~ % doas sysrc zrepl_enable=YES
zrepl_enable:  -> YES
paul@f0:~ % doas service `zrepl` start
Starting zrepl.

# On f1
paul@f1:~ % doas sysrc zrepl_enable=YES
zrepl_enable:  -> YES
paul@f1:~ % doas service `zrepl` start
Starting zrepl.

To check the replication status, we run:

# On f0, check `zrepl` status (use raw mode for non-tty)
paul@f0:~ % doas pkg install jq
paul@f0:~ % doas zrepl status --mode raw | grep -A2 "Replication" | jq .
"Replication":{"StartAt":"2025-07-01T22:31:48.712143123+03:00"...

# Check if services are running
paul@f0:~ % doas service zrepl status
zrepl is running as pid 2649.

paul@f1:~ % doas service zrepl status
zrepl is running as pid 2574.

# Check for `zrepl` snapshots on source
paul@f0:~ % doas zfs list -t snapshot -r zdata/enc | grep zrepl
zdata/enc@zrepl_20250701_193148_000    0B      -   176K  -

# On f1, verify the replicated datasets  
paul@f1:~ % doas zfs list -r zdata | grep f0
zdata/f0             576K   899G   200K  none
zdata/f0/zdata       376K   899G   200K  none
zdata/f0/zdata/enc   176K   899G   176K  none

# Check replicated snapshots on f1
paul@f1:~ % doas zfs list -t snapshot -r zdata | grep zrepl
zdata/f0/zdata/enc@zrepl_20250701_193148_000     0B      -   176K  -
zdata/f0/zdata/enc@zrepl_20250701_194148_000     0B      -   176K  -
.
.
.

Monitoring replication

You can monitor the replication progress with:

paul@f0:~ % doas zrepl status

zrepl status

With this setup, both `zdata/enc/nfsdata` and `zroot/bhyve/fedora` on `f0` will be automatically replicated to `f1` every 1 minute (or 10 minutes in the case of the Fedora VM), with encrypted snapshots preserved on both sides. The pruning policy ensures that we keep the last 10 snapshots while managing disk space efficiently.

The replicated data appears on `f1` under `zdata/sink/` with the source host and dataset hierarchy preserved:

`zdata/enc/nfsdata` → `zdata/sink/f0/zdata/enc/nfsdata`
`zroot/bhyve/fedora` → `zdata/sink/f0/zroot/bhyve/fedora`

This is by design - `zrepl` preserves the complete path from the source to ensure there are no conflicts when replicating from multiple sources.

Verifying replication after reboot

The `zrepl` service is configured to start automatically at boot. After rebooting both hosts:

paul@f0:~ % uptime
11:17PM  up 1 min, 0 users, load averages: 0.16, 0.06, 0.02

paul@f0:~ % doas service `zrepl` status
zrepl is running as pid 2366.

paul@f1:~ % doas service `zrepl` status
zrepl is running as pid 2309.

# Check that new snapshots are being created and replicated
paul@f0:~ % doas zfs list -t snapshot | grep `zrepl` | tail -2
zdata/enc/nfsdata@zrepl_20250701_202530_000                0B      -   200K  -
zroot/bhyve/fedora@zrepl_20250701_202530_000               0B      -  2.97G  -
.
.
.

paul@f1:~ % doas zfs list -t snapshot -r zdata/sink | grep 202530
zdata/sink/f0/zdata/enc/nfsdata@zrepl_20250701_202530_000      0B      -   176K  -
zdata/sink/f0/zroot/bhyve/fedora@zrepl_20250701_202530_000     0B      -  2.97G  -
.
.
.

The timestamps confirm that replication resumed automatically after the reboot, ensuring continuous data protection. We can also write a test file to the NFS data directory on `f0` and verify whether it appears on `f1` after a minute.

Understanding Failover Limitations and Design Decisions

Our system intentionally fails over to a read-only copy of the replica in the event of the primary's failure. This is due to the nature of `zrepl`, which only replicates data in one direction. If we mount the data set on the sink node in read-write mode, it would cause the ZFS dataset to diverge from the original, and the replication would break. It can still be mounted read-write on the sink node in case of a genuine issue on the primary node, but that step is left intentionally manual. Therefore, we don't need to fix the replication later on manually.

So in summary:

Split-brain prevention: Automatic failover to a read-write copy can cause both nodes to become active simultaneously if network communication fails. This leads to data divergence that's extremely difficult to resolve.
False positive protection: Temporary network issues or high load can trigger unwanted failovers. Manual intervention ensures that failovers occur only when truly necessary.
Data integrity over availability: For storage systems, data consistency is paramount. A few minutes of downtime is preferable to data corruption in this specific use case.
Simplified recovery: With manual failover, you always know which dataset is authoritative, making recovery more straightforward.

Mounting the NFS datasets

To make the NFS data accessible on both nodes, we need to mount it. On `f0`, this is straightforward:

# On f0 - set mountpoint for the primary nfsdata
paul@f0:~ % doas zfs set mountpoint=/data/nfs zdata/enc/nfsdata
paul@f0:~ % doas mkdir -p /data/nfs

# Verify it's mounted
paul@f0:~ % df -h /data/nfs
Filesystem           Size    Used   Avail Capacity  Mounted on
zdata/enc/nfsdata    899G    204K    899G     0%    /data/nfs

On `f1`, we need to handle the encryption key and mount the standby copy:

# On f1 - first check encryption status
paul@f1:~ % doas zfs get keystatus zdata/sink/f0/zdata/enc/nfsdata
NAME                             PROPERTY   VALUE        SOURCE
zdata/sink/f0/zdata/enc/nfsdata  keystatus  unavailable  -

# Load the encryption key (using f0's key stored on the USB)
paul@f1:~ % doas zfs load-key -L file:///keys/f0.lan.buetow.org:zdata.key \
    zdata/sink/f0/zdata/enc/nfsdata

# Set mountpoint and mount (same path as f0 for easier failover)
paul@f1:~ % doas mkdir -p /data/nfs
paul@f1:~ % doas zfs set mountpoint=/data/nfs zdata/sink/f0/zdata/enc/nfsdata
paul@f1:~ % doas zfs mount zdata/sink/f0/zdata/enc/nfsdata

# Make it read-only to prevent accidental writes that would break replication
paul@f1:~ % doas zfs set readonly=on zdata/sink/f0/zdata/enc/nfsdata

# Verify
paul@f1:~ % df -h /data/nfs
Filesystem                         Size    Used   Avail Capacity  Mounted on
zdata/sink/f0/zdata/enc/nfsdata    896G    204K    896G     0%    /data/nfs

Note: The dataset is mounted at the same path (`/data/nfs`) on both hosts to simplify failover procedures. The dataset on `f1` is set to `readonly=on` to prevent accidental modifications, which, as mentioned earlier, would break replication. If we did, replication from `f0` to `f1` would fail like this:

cannot receive incremental stream: destination zdata/sink/f0/zdata/enc/nfsdata has been modified since most recent snapshot

To fix a broken replication after accidental writes, we can do:

# Option 1: Rollback to the last common snapshot (loses local changes)
paul@f1:~ % doas zfs rollback zdata/sink/f0/zdata/enc/nfsdata@zrepl_20250701_204054_000

# Option 2: Make it read-only to prevent accidents again
paul@f1:~ % doas zfs set readonly=on zdata/sink/f0/zdata/enc/nfsdata

And replication should work again!

Troubleshooting: Files not appearing in replication

If you write files to `/data/nfs/` on `f0` but they don't appear on `f1`, check if the dataset is mounted on `f0`?

paul@f0:~ % doas zfs list -o name,mountpoint,mounted | grep nfsdata
zdata/enc/nfsdata                             /data/nfs             yes

If it shows `no`, the dataset isn't mounted! This means files are being written to the root filesystem, not ZFS. Next, we should check whether the encryption key is loaded:

paul@f0:~ % doas zfs get keystatus zdata/enc/nfsdata
NAME               PROPERTY   VALUE        SOURCE
zdata/enc/nfsdata  keystatus  available    -
# If "unavailable", load the key:
paul@f0:~ % doas zfs load-key -L file:///keys/f0.lan.buetow.org:zdata.key zdata/enc/nfsdata
paul@f0:~ % doas zfs mount zdata/enc/nfsdata

You can also verify that files are in the snapshot (not just the directory):

paul@f0:~ % ls -la /data/nfs/.zfs/snapshot/zrepl_*/

This issue commonly occurs after a reboot if the encryption keys aren't configured to load automatically.

Configuring automatic key loading on boot

To ensure all additional encrypted datasets are mounted automatically after reboot as well, we do:

# On f0 - configure all encrypted datasets
paul@f0:~ % doas sysrc zfskeys_enable=YES
zfskeys_enable: YES -> YES
paul@f0:~ % doas sysrc zfskeys_datasets="zdata/enc zdata/enc/nfsdata zroot/bhyve"
zfskeys_datasets:  -> zdata/enc zdata/enc/nfsdata zroot/bhyve

# Set correct key locations for all datasets
paul@f0:~ % doas zfs set \
  keylocation=file:///keys/f0.lan.buetow.org:zdata.key zdata/enc/nfsdata

# On f1 - include the replicated dataset
paul@f1:~ % doas sysrc zfskeys_enable=YES
zfskeys_enable: YES -> YES
paul@f1:~ % doas sysrc \
  zfskeys_datasets="zdata/enc zroot/bhyve zdata/sink/f0/zdata/enc/nfsdata"
zfskeys_datasets:  -> zdata/enc zroot/bhyve zdata/sink/f0/zdata/enc/nfsdata

# Set key location for replicated dataset
paul@f1:~ % doas zfs set \
  keylocation=file:///keys/f0.lan.buetow.org:zdata.key zdata/sink/f0/zdata/enc/nfsdata

Important notes:

Each encryption root needs its own key load entry
The replicated dataset on `f1` uses the same encryption key as the source on `f0`
Always verify datasets are mounted after reboot with `zfs list -o name,mounted`
Critical: Always ensure the replicated dataset on `f1` remains read-only with `doas zfs set readonly=on zdata/sink/f0/zdata/enc/nfsdata`

Troubleshooting: zrepl Replication Not Working

If `zrepl` replication is not working, here's a systematic approach to diagnose and fix common issues:

Check if zrepl Services are Running

First, verify that `zrepl` is running on both nodes:

# Check service status on both f0 and f1
paul@f0:~ % doas service zrepl status
paul@f1:~ % doas service zrepl status

# If not running, start the service
paul@f0:~ % doas service zrepl start
paul@f1:~ % doas service zrepl start

Check zrepl Status for Errors

Use the status command to see detailed error information:

# Check detailed status (use --mode raw for non-tty environments)
paul@f0:~ % doas zrepl status --mode raw

# Look for error messages in the replication section
# Common errors include "no common snapshot" or connection failures

Fixing "No Common Snapshot" Errors

This is the most common replication issue, typically occurring when:

The receiver has existing snapshots that don't match the sender
Different snapshot naming schemes are in use
The receiver dataset was created independently

*Error message example:**

no common snapshot or suitable bookmark between sender and receiver

*Solution: Clean up conflicting snapshots on receiver**

# First, identify the destination dataset on f1
paul@f1:~ % doas zfs list | grep sink

# Check existing snapshots on the problematic dataset
paul@f1:~ % doas zfs list -t snapshot | grep nfsdata

# If you see snapshots with different naming (e.g., @daily-*, @weekly-*)
# these conflict with zrepl's @zrepl_* snapshots

# Destroy the entire destination dataset to allow clean replication
paul@f1:~ % doas zfs destroy -r zdata/sink/f0/zdata/enc/nfsdata

# For VM replication, do the same for the fedora dataset
paul@f1:~ % doas zfs destroy -r zdata/sink/f0/zroot/bhyve/fedora

# Wake up zrepl to start fresh replication
paul@f0:~ % doas zrepl signal wakeup f0_to_f1_nfsdata
paul@f0:~ % doas zrepl signal wakeup f0_to_f1_fedora

# Check replication status
paul@f0:~ % doas zrepl status --mode raw

*Verification that replication is working:**

# Look for "stepping" state and active zfs send processes
paul@f0:~ % doas zrepl status --mode raw | grep -A5 "State.*stepping"

# Check for active ZFS commands
paul@f0:~ % doas zrepl status --mode raw | grep -A10 "ZFSCmds.*Active"

# Monitor progress - bytes replicated should be increasing
paul@f0:~ % doas zrepl status --mode raw | grep BytesReplicated

Network Connectivity Issues

If replication fails to connect:

# Test connectivity between nodes
paul@f0:~ % nc -zv 192.168.2.131 8888

# Check if zrepl is listening on f1
paul@f1:~ % doas netstat -an | grep 8888

# Verify WireGuard tunnel is working
paul@f0:~ % ping 192.168.2.131

Encryption Key Issues

If encrypted replication fails:

# Verify encryption keys are available on both nodes
paul@f0:~ % doas zfs get keystatus zdata/enc/nfsdata
paul@f1:~ % doas zfs get keystatus zdata/sink/f0/zdata/enc/nfsdata

# Load keys if unavailable
paul@f1:~ % doas zfs load-key -L file:///keys/f0.lan.buetow.org:zdata.key \
    zdata/sink/f0/zdata/enc/nfsdata

Monitoring Ongoing Replication

After fixing issues, monitor replication health:

# Monitor replication progress (run repeatedly to check status)
paul@f0:~ % doas zrepl status --mode raw | grep -A10 BytesReplicated

# Or install watch from ports and use it
paul@f0:~ % doas pkg install watch
paul@f0:~ % watch -n 5 'doas zrepl status --mode raw | grep -A10 BytesReplicated'

# Check for new snapshots being created
paul@f0:~ % doas zfs list -t snapshot | grep zrepl | tail -5

# Verify snapshots appear on receiver
paul@f1:~ % doas zfs list -t snapshot -r zdata/sink | grep zrepl | tail -5

This troubleshooting process resolves the most common `zrepl` issues and ensures continuous data replication between your storage nodes.

CARP (Common Address Redundancy Protocol)

High availability is crucial for storage systems. If the storage server goes down, all NFS clients (which will also be Kubernetes pods later on in this series) lose access to their persistent data. CARP provides a solution by creating a virtual IP address that automatically migrates to a different server during failures. This means that clients point to that VIP for NFS mounts and are always contacting the current primary node.

How CARP Works

In our case, CARP allows two hosts (`f0` and `f1`) to share a virtual IP address (VIP). The hosts communicate using multicast to elect a MASTER, while the other remain as BACKUP. When the MASTER fails, the BACKUP automatically promotes itself, and the VIP is reassigned to the new MASTER. This happens within seconds.

Key benefits for our storage system:

Automatic failover: No manual intervention is required for basic failures, although there are a few limitations. The backup will have read-only access to the available data by default, as we have already learned.
Transparent to clients: Pods continue using the same IP address
Works with `stunnel`: Behind the VIP, there will be a `stunnel` process running, which ensures encrypted connections follow the active server.

FreeBSD CARP

Stunnel

Configuring CARP

First, we add the CARP configuration to `/etc/rc.conf` on both `f0` and `f1`:

# The virtual IP 192.168.1.138 will float between f0 and f1
ifconfig_re0_alias0="inet vhid 1 pass testpass alias 192.168.1.138/32"

Whereas:

`vhid 1`: Virtual Host ID - must match on all CARP members
`pass testpass`: Password for CARP authentication (if you follow this, use a different password!)
`alias 192.168.1.138/32`: The virtual IP address with a /32 netmask

Next, update `/etc/hosts` on all nodes (`f0`, `f1`, `f2`, `r0`, `r1`, `r2`) to resolve the VIP hostname:

192.168.2.138 f3s-storage-ha f3s-storage-ha.wg0 f3s-storage-ha.wg0.wan.buetow.org

This allows clients to connect to `f3s-storage-ha` regardless of which physical server is currently the MASTER.

CARP State Change Notifications

To correctly manage services during failover, we need to detect CARP state changes. FreeBSD's devd system can notify us when CARP transitions between MASTER and BACKUP states.

Add this to `/etc/devd.conf` on both `f0` and `f1`:

paul@f0:~ % cat <

Next, we create the CARP control script that will restart stunnel when the CARP state changes:

paul@f0:~ % doas tee /usr/local/bin/carpcontrol.sh <<'EOF'
#!/bin/sh
# CARP state change control script

case "$1" in
    MASTER)
        logger "CARP state changed to MASTER, starting services"
        ;;
    BACKUP)
        logger "CARP state changed to BACKUP, stopping services"
        ;;
    *)
        logger "CARP state changed to $1 (unhandled)"
        ;;
esac
EOF

paul@f0:~ % doas chmod +x /usr/local/bin/carpcontrol.sh

# Copy the same script to f1
paul@f0:~ % scp /usr/local/bin/carpcontrol.sh f1:/tmp/
paul@f1:~ % doas mv /tmp/carpcontrol.sh /usr/local/bin/
paul@f1:~ % doas chmod +x /usr/local/bin/carpcontrol.sh


Note that `carpcontrol.sh` doesn't do anything useful yet. We will provide more details (including starting and stopping services upon failover) later in this blog post.

To enable CARP in `/boot/loader.conf`, run:

paul@f0:~ % echo 'carp_load="YES"' | doas tee -a /boot/loader.conf
carp_load="YES"
paul@f1:~ % echo 'carp_load="YES"' | doas tee -a /boot/loader.conf  
carp_load="YES"


Then reboot both hosts or run `doas kldload carp` to load the module immediately. 

NFS Server Configuration

With ZFS replication in place, we can now set up NFS servers on both `f0` and `f1` to export the replicated data. Since native NFS over TLS (RFC 9289) has compatibility issues between Linux and FreeBSD (not digging into the details here, but I couldn't get it to work), we'll use stunnel to provide encryption.

Setting up NFS on `f0` (Primary)

First, enable the NFS services in rc.conf:

paul@f0:~ % doas sysrc nfs_server_enable=YES
nfs_server_enable: YES -> YES
paul@f0:~ % doas sysrc nfsv4_server_enable=YES
nfsv4_server_enable: YES -> YES
paul@f0:~ % doas sysrc nfsuserd_enable=YES
nfsuserd_enable: YES -> YES
paul@f0:~ % doas sysrc nfsuserd_flags="-domain lan.buetow.org"
nfsuserd_flags: "" -> "-domain lan.buetow.org"
paul@f0:~ % doas sysrc mountd_enable=YES
mountd_enable: NO -> YES
paul@f0:~ % doas sysrc rpcbind_enable=YES
rpcbind_enable: NO -> YES


Update: 08.08.2025: I've added the domain to `nfsuserd_flags`

And we also create a dedicated directory for Kubernetes volumes:

# First, ensure the dataset is mounted
paul@f0:~ % doas zfs get mounted zdata/enc/nfsdata
NAME               PROPERTY  VALUE    SOURCE
zdata/enc/nfsdata  mounted   yes      -

# Create the k3svolumes directory
paul@f0:~ % doas mkdir -p /data/nfs/k3svolumes
paul@f0:~ % doas chmod 755 /data/nfs/k3svolumes


We also create the `/etc/exports` file. Since we're using stunnel for encryption, ALL clients must connect through stunnel, which appears as localhost (`127.0.0.1`) to the NFS server:

paul@f0:~ % doas tee /etc/exports <<'EOF'
V4: /data/nfs -sec=sys
/data/nfs -alldirs -maproot=root -network 127.0.0.1 -mask 255.255.255.255
EOF


The exports configuration:


`V4: /data/nfs -sec=sys`: Sets the NFSv4 root directory to /data/nfs
`-maproot=root`: Maps root user from client to root on server
`-network 127.0.0.1`: Only accepts connections from localhost (`stunnel`)


To start the NFS services, we run:

paul@f0:~ % doas service rpcbind start
Starting rpcbind.
paul@f0:~ % doas service mountd start
Starting mountd.
paul@f0:~ % doas service nfsd start
Starting nfsd.
paul@f0:~ % doas service nfsuserd start
Starting nfsuserd.


Configuring Stunnel for NFS Encryption with CARP Failover

Using stunnel with client certificate authentication for NFS encryption provides several advantages:


Compatibility: Works with any NFS version and between different operating systems
Strong encryption: Uses TLS/SSL with configurable cipher suites
Transparent: Applications don't need modification, encryption happens at the transport layer
Performance: Minimal overhead (~2% in benchmarks)
Flexibility: Can encrypt any TCP-based protocol, not just NFS
Strong Authentication: Client certificates provide cryptographic proof of identity
Access Control: Only clients with valid certificates signed by your CA can connect
Certificate Revocation: You can revoke access by removing certificates from the CA


Stunnel integrates seamlessly with our CARP setup:

                    CARP VIP (192.168.1.138)
                           |
    f0 (MASTER) ←---------→|←---------→ f1 (BACKUP)
    stunnel:2323           |           stunnel:stopped
    nfsd:2049              |           nfsd:stopped
                           |
                    Clients connect here


The key insight is that stunnel binds to the CARP VIP. When CARP fails over, the VIP is moved to the new master, and stunnel starts there automatically. Clients maintain their connection to the same IP throughout.

Creating a Certificate Authority for Client Authentication

First, create a CA to sign both server and client certificates:

# On f0 - Create CA
paul@f0:~ % doas mkdir -p /usr/local/etc/stunnel/ca
paul@f0:~ % cd /usr/local/etc/stunnel/ca
paul@f0:~ % doas openssl genrsa -out ca-key.pem 4096
paul@f0:~ % doas openssl req -new -x509 -days 3650 -key ca-key.pem -out ca-cert.pem \
  -subj '/C=US/ST=State/L=City/O=F3S Storage/CN=F3S Stunnel CA'

# Create server certificate
paul@f0:~ % cd /usr/local/etc/stunnel
paul@f0:~ % doas openssl genrsa -out server-key.pem 4096
paul@f0:~ % doas openssl req -new -key server-key.pem -out server.csr \
  -subj '/C=US/ST=State/L=City/O=F3S Storage/CN=f3s-storage-ha.lan'
paul@f0:~ % doas openssl x509 -req -days 3650 -in server.csr -CA ca/ca-cert.pem \
  -CAkey ca/ca-key.pem -CAcreateserial -out server-cert.pem

# Create client certificates for authorised clients
paul@f0:~ % cd /usr/local/etc/stunnel/ca
paul@f0:~ % doas sh -c 'for client in r0 r1 r2 earth; do 
  openssl genrsa -out ${client}-key.pem 4096
  openssl req -new -key ${client}-key.pem -out ${client}.csr \
    -subj "/C=US/ST=State/L=City/O=F3S Storage/CN=${client}.lan.buetow.org"
  openssl x509 -req -days 3650 -in ${client}.csr -CA ca-cert.pem \
    -CAkey ca-key.pem -CAcreateserial -out ${client}-cert.pem
done'


Install and Configure Stunnel on `f0`

# Install stunnel
paul@f0:~ % doas pkg install -y stunnel

# Configure stunnel server with client certificate authentication
paul@f0:~ % doas tee /usr/local/etc/stunnel/stunnel.conf <<'EOF'
cert = /usr/local/etc/stunnel/server-cert.pem
key = /usr/local/etc/stunnel/server-key.pem

setuid = stunnel
setgid = stunnel

[nfs-tls]
accept = 192.168.1.138:2323
connect = 127.0.0.1:2049
CAfile = /usr/local/etc/stunnel/ca/ca-cert.pem
verify = 2
requireCert = yes
EOF

# Enable and start stunnel
paul@f0:~ % doas sysrc stunnel_enable=YES
stunnel_enable:  -> YES
paul@f0:~ % doas service stunnel start
Starting stunnel.

# Restart stunnel to apply the CARP VIP binding
paul@f0:~ % doas service stunnel restart
Stopping stunnel.
Starting stunnel.


The configuration includes:


`verify = 2`: Verify client certificate and fail if not provided
`requireCert = yes`: Client must present a valid certificate
`CAfile`: Path to the CA certificate that signed the client certificates


Setting up NFS on `f1` (Standby)

Repeat the same configuration on `f1`:

paul@f1:~ % doas sysrc nfs_server_enable=YES
nfs_server_enable: NO -> YES
paul@f1:~ % doas sysrc nfsv4_server_enable=YES
nfsv4_server_enable: NO -> YES
paul@f1:~ % doas sysrc nfsuserd_enable=YES
nfsuserd_enable: NO -> YES
paul@f1:~ % doas sysrc mountd_enable=YES
mountd_enable: NO -> YES
paul@f1:~ % doas sysrc rpcbind_enable=YES
rpcbind_enable: NO -> YES

paul@f1:~ % doas tee /etc/exports <<'EOF'
V4: /data/nfs -sec=sys
/data/nfs -alldirs -maproot=root -network 127.0.0.1 -mask 255.255.255.255
EOF

paul@f1:~ % doas service rpcbind start
Starting rpcbind.
paul@f1:~ % doas service mountd start
Starting mountd.
paul@f1:~ % doas service nfsd start
Starting nfsd.
paul@f1:~ % doas service nfsuserd start
Starting nfsuserd.


And to configure stunnel on `f1`, we run:

# Install stunnel
paul@f1:~ % doas pkg install -y stunnel

# Copy certificates from f0
paul@f0:~ % doas tar -cf /tmp/stunnel-certs.tar \
  -C /usr/local/etc/stunnel server-cert.pem server-key.pem ca
paul@f0:~ % scp /tmp/stunnel-certs.tar f1:/tmp/

paul@f1:~ % cd /usr/local/etc/stunnel && doas tar -xf /tmp/stunnel-certs.tar

# Configure stunnel server on f1 with client certificate authentication
paul@f1:~ % doas tee /usr/local/etc/stunnel/stunnel.conf <<'EOF'
cert = /usr/local/etc/stunnel/server-cert.pem
key = /usr/local/etc/stunnel/server-key.pem

setuid = stunnel
setgid = stunnel

[nfs-tls]
accept = 192.168.1.138:2323
connect = 127.0.0.1:2049
CAfile = /usr/local/etc/stunnel/ca/ca-cert.pem
verify = 2
requireCert = yes
EOF

# Enable and start stunnel
paul@f1:~ % doas sysrc stunnel_enable=YES
stunnel_enable:  -> YES
paul@f1:~ % doas service stunnel start
Starting stunnel.

# Restart stunnel to apply the CARP VIP binding
paul@f1:~ % doas service stunnel restart
Stopping stunnel.
Starting stunnel.


CARP Control Script for Clean Failover

With stunnel configured to bind to the CARP VIP (192.168.1.138), only the server that is currently the CARP MASTER will accept stunnel connections. This provides automatic failover for encrypted NFS:


When `f0` is CARP MASTER: stunnel on `f0` accepts connections on `192.168.1.138:2323`
When `f1` becomes CARP MASTER: stunnel on `f1` starts accepting connections on `192.168.1.138:2323`
The backup server's stunnel process will fail to bind to the VIP and won't accept connections


This ensures that clients always connect to the active NFS server through the CARP VIP. To ensure clean failover behaviour and prevent stale file handles, we'll update our `carpcontrol.sh` script so that:


Stops NFS services on BACKUP nodes (preventing split-brain scenarios)
Starts NFS services only on the MASTER node
Manages stunnel binding to the CARP VIP


This approach ensures clients can only connect to the active server, eliminating stale handles from the inactive server:

# Create CARP control script on both f0 and f1
paul@f0:~ % doas tee /usr/local/bin/carpcontrol.sh <<'EOF'
#!/bin/sh
# CARP state change control script

HOSTNAME=`hostname`

if [ ! -f /data/nfs/nfs.DO_NOT_REMOVE ]; then
    logger '/data/nfs not mounted, mounting it now!'
    if [ "$HOSTNAME" = 'f0.lan.buetow.org' ]; then
        zfs load-key -L file:///keys/f0.lan.buetow.org:zdata.key zdata/enc/nfsdata
        zfs set mountpoint=/data/nfs zdata/enc/nfsdata
    else
        zfs load-key -L file:///keys/f0.lan.buetow.org:zdata.key zdata/sink/f0/zdata/enc/nfsdata
        zfs set mountpoint=/data/nfs zdata/sink/f0/zdata/enc/nfsdata
        zfs mount zdata/sink/f0/zdata/enc/nfsdata
        zfs set readonly=on zdata/sink/f0/zdata/enc/nfsdata
    fi
    service nfsd stop 2>&1
    service mountd stop 2>&1
fi


case "$1" in
    MASTER)
        logger "CARP state changed to MASTER, starting services"
        service rpcbind start >/dev/null 2>&1
        service mountd start >/dev/null 2>&1
        service nfsd start >/dev/null 2>&1
        service nfsuserd start >/dev/null 2>&1
        service stunnel restart >/dev/null 2>&1
        logger "CARP MASTER: NFS and stunnel services started"
        ;;
    BACKUP)
        logger "CARP state changed to BACKUP, stopping services"
        service stunnel stop >/dev/null 2>&1
        service nfsd stop >/dev/null 2>&1
        service mountd stop >/dev/null 2>&1
        service nfsuserd stop >/dev/null 2>&1
        logger "CARP BACKUP: NFS and stunnel services stopped"
        ;;
    *)
        logger "CARP state changed to $1 (unhandled)"
        ;;
esac
EOF

paul@f0:~ % doas chmod +x /usr/local/bin/carpcontrol.sh


CARP Management Script

To simplify CARP state management and failover testing, create this helper script on both `f0` and `f1`:

# Create the CARP management script
paul@f0:~ % doas tee /usr/local/bin/carp <<'EOF'
#!/bin/sh
# CARP state management script
# Usage: carp [master|backup|auto-failback enable|auto-failback disable]
# Without arguments: shows current state

# Find the interface with CARP configured
CARP_IF=$(ifconfig -l | xargs -n1 | while read if; do
    ifconfig "$if" 2>/dev/null | grep -q "carp:" && echo "$if" && break
done)

if [ -z "$CARP_IF" ]; then
    echo "Error: No CARP interface found"
    exit 1
fi

# Get CARP VHID
VHID=$(ifconfig "$CARP_IF" | grep "carp:" | sed -n 's/.*vhid \([0-9]*\).*/\1/p')

if [ -z "$VHID" ]; then
    echo "Error: Could not determine CARP VHID"
    exit 1
fi

# Function to get the current state
get_state() {
    ifconfig "$CARP_IF" | grep "carp:" | awk '{print $2}'
}

# Check for auto-failback block file
BLOCK_FILE="/data/nfs/nfs.NO_AUTO_FAILBACK"
check_auto_failback() {
    if [ -f "$BLOCK_FILE" ]; then
        echo "WARNING: Auto-failback is DISABLED (file exists: $BLOCK_FILE)"
    fi
}

# Main logic
case "$1" in
    "")
        # No argument - show current state
        STATE=$(get_state)
        echo "CARP state on $CARP_IF (vhid $VHID): $STATE"
        check_auto_failback
        ;;
    master)
        # Force to MASTER state
        echo "Setting CARP to MASTER state..."
        ifconfig "$CARP_IF" vhid "$VHID" state master
        sleep 1
        STATE=$(get_state)
        echo "CARP state on $CARP_IF (vhid $VHID): $STATE"
        check_auto_failback
        ;;
    backup)
        # Force to BACKUP state
        echo "Setting CARP to BACKUP state..."
        ifconfig "$CARP_IF" vhid "$VHID" state backup
        sleep 1
        STATE=$(get_state)
        echo "CARP state on $CARP_IF (vhid $VHID): $STATE"
        check_auto_failback
        ;;
    auto-failback)
        case "$2" in
            enable)
                if [ -f "$BLOCK_FILE" ]; then
                    rm "$BLOCK_FILE"
                    echo "Auto-failback ENABLED (removed $BLOCK_FILE)"
                else
                    echo "Auto-failback was already enabled"
                fi
                ;;
            disable)
                if [ ! -f "$BLOCK_FILE" ]; then
                    touch "$BLOCK_FILE"
                    echo "Auto-failback DISABLED (created $BLOCK_FILE)"
                else
                    echo "Auto-failback was already disabled"
                fi
                ;;
            *)
                echo "Usage: $0 auto-failback [enable|disable]"
                echo "  enable:  Remove block file to allow automatic failback"
                echo "  disable: Create block file to prevent automatic failback"
                exit 1
                ;;
        esac
        ;;
    *)
        echo "Usage: $0 [master|backup|auto-failback enable|auto-failback disable]"
        echo "  Without arguments: show current CARP state"
        echo "  master: force this node to become CARP MASTER"
        echo "  backup: force this node to become CARP BACKUP"
        echo "  auto-failback enable:  allow automatic failback to f0"
        echo "  auto-failback disable: prevent automatic failback to f0"
        exit 1
        ;;
esac
EOF

paul@f0:~ % doas chmod +x /usr/local/bin/carp

# Copy to f1 as well
paul@f0:~ % scp /usr/local/bin/carp f1:/tmp/
paul@f1:~ % doas cp /tmp/carp /usr/local/bin/carp && doas chmod +x /usr/local/bin/carp


Now you can easily manage CARP states and auto-failback:

# Check current CARP state
paul@f0:~ % doas carp
CARP state on re0 (vhid 1): MASTER

# If auto-failback is disabled, you'll see a warning
paul@f0:~ % doas carp
CARP state on re0 (vhid 1): MASTER
WARNING: Auto-failback is DISABLED (file exists: /data/nfs/nfs.NO_AUTO_FAILBACK)

# Force f0 to become BACKUP (triggers failover to f1)
paul@f0:~ % doas carp backup
Setting CARP to BACKUP state...
CARP state on re0 (vhid 1): BACKUP

# Disable auto-failback (useful for maintenance)
paul@f0:~ % doas carp auto-failback disable
Auto-failback DISABLED (created /data/nfs/nfs.NO_AUTO_FAILBACK)

# Enable auto-failback
paul@f0:~ % doas carp auto-failback enable
Auto-failback ENABLED (removed /data/nfs/nfs.NO_AUTO_FAILBACK)


Automatic Failback After Reboot

When `f0` reboots (planned or unplanned), `f1` takes over as CARP MASTER. To ensure `f0` automatically reclaims its primary role once it's fully operational, we'll implement an automatic failback mechanism. With:

paul@f0:~ % doas tee /usr/local/bin/carp-auto-failback.sh <<'EOF'
#!/bin/sh
# CARP automatic failback script for f0
# Ensures f0 reclaims MASTER role after reboot when storage is ready

LOGFILE="/var/log/carp-auto-failback.log"
MARKER_FILE="/data/nfs/nfs.DO_NOT_REMOVE"
BLOCK_FILE="/data/nfs/nfs.NO_AUTO_FAILBACK"

log_message() {
    echo "$(date '+%Y-%m-%d %H:%M:%S') - $1" >> "$LOGFILE"
}

# Check if we're already MASTER
CURRENT_STATE=$(/usr/local/bin/carp | awk '{print $NF}')
if [ "$CURRENT_STATE" = "MASTER" ]; then
    exit 0
fi

# Check if /data/nfs is mounted
if ! mount | grep -q "on /data/nfs "; then
    log_message "SKIP: /data/nfs not mounted"
    exit 0
fi

# Check if the marker file exists
# (identifies that the ZFS data set is properly mounted)
if [ ! -f "$MARKER_FILE" ]; then
    log_message "SKIP: Marker file $MARKER_FILE not found"
    exit 0
fi

# Check if failback is blocked (for maintenance)
if [ -f "$BLOCK_FILE" ]; then
    log_message "SKIP: Failback blocked by $BLOCK_FILE"
    exit 0
fi

# Check if NFS services are running (ensure we're fully ready)
if ! service nfsd status >/dev/null 2>&1; then
    log_message "SKIP: NFS services not yet running"
    exit 0
fi

# All conditions met - promote to MASTER
log_message "CONDITIONS MET: Promoting to MASTER (was $CURRENT_STATE)"
/usr/local/bin/carp master

# Log result
sleep 2
NEW_STATE=$(/usr/local/bin/carp | awk '{print $NF}')
log_message "Failback complete: State is now $NEW_STATE"

# If successful, log to the system log too
if [ "$NEW_STATE" = "MASTER" ]; then
    logger "CARP: f0 automatically reclaimed MASTER role"
fi
EOF

paul@f0:~ % doas chmod +x /usr/local/bin/carp-auto-failback.sh


The marker file identifies that the ZFS data set is mounted correctly. We create it with:

paul@f0:~ % doas touch /data/nfs/nfs.DO_NOT_REMOVE


We add a cron job to check every minute:

paul@f0:~ % echo "* * * * * /usr/local/bin/carp-auto-failback.sh" | doas crontab -


The enhanced CARP script provides integrated control over auto-failback. To temporarily turn off automatic failback (e.g., for `f0` maintenance), we run:

paul@f0:~ % doas carp auto-failback disable
Auto-failback DISABLED (created /data/nfs/nfs.NO_AUTO_FAILBACK)


And to re-enable it:

paul@f0:~ % doas carp auto-failback enable
Auto-failback ENABLED (removed /data/nfs/nfs.NO_AUTO_FAILBACK)


To check whether auto-failback is enabled, we run:

paul@f0:~ % doas carp
CARP state on re0 (vhid 1): MASTER
# If disabled, you'll see: WARNING: Auto-failback is DISABLED


The failback attempts are logged to `/var/log/carp-auto-failback.log`!

So, in summary:


After f`0 `reboots: `f1` is MASTER, f`0 `boots as BACKUP
Cron runs every minute: Checks if conditions are met (Is `f0` currently BACKUP? (don't run if already MASTER)), (Is /data/nfs mounted? (ZFS datasets are ready)), (Does marker file exist? (confirms this is primary storage)), (Is failback blocked? (admin can prevent failback)), (Are NFS services running? (system is fully ready))
Failback occurs: Typically 2-3 minutes after boot completes
Logging: All attempts logged for troubleshooting


This ensures `f0` automatically resumes its role as primary storage server after any reboot, while providing administrative control when needed.

Client Configuration for NFS via Stunnel

To mount NFS shares with stunnel encryption, clients must install and configure stunnel using their client certificates.

Configuring Rocky Linux Clients (`r0`, `r1`, `r2`)

On the Rocky Linux VMs, we run:

# Install stunnel on client (example for `r0`)
[root@r0 ~]# dnf install -y stunnel nfs-utils

# Copy client certificate and CA certificate from f0
[root@r0 ~]# scp f0:/usr/local/etc/stunnel/ca/r0-key.pem /etc/stunnel/
[root@r0 ~]# scp f0:/usr/local/etc/stunnel/ca/ca-cert.pem /etc/stunnel/

# Configure stunnel client with certificate authentication
[root@r0 ~]# tee /etc/stunnel/stunnel.conf <<'EOF'
cert = /etc/stunnel/r0-key.pem
CAfile = /etc/stunnel/ca-cert.pem
client = yes
verify = 2

[nfs-ha]
accept = 127.0.0.1:2323
connect = 192.168.1.138:2323
EOF

# Enable and start stunnel
[root@r0 ~]# systemctl enable --now stunnel

# Repeat for r1 and r2 with their respective certificates


Note: Each client must use its certificate file (`r0-key.pem`, `r1-key.pem`, `r2-key.pem`, or `earth-key.pem` - the latter is for my Laptop, which can also mount the NFS shares).

NFSv4 user mapping config on Rocky

Update: This section was added 08.08.2025!

For this, we need to set the `Domain` in `/etc/idmapd.conf` on all 3 Rocky hosts to `lan.buetow.org` (remember, earlier in this blog post we set the `nfsuserd` domain on the NFS server side to `lan.buetow.org` as well!)

[General]

Domain = lan.buetow.org
.
.
.


And afterwards, we need to run the following on all 3 Rocky hosts::

[root@r0 ~]# systemctl enable --now nfs-idmapd
[root@r0 ~]# systemctl enable --now nfs-client.target


and then, safest, reboot those.

Testing NFS Mount with Stunnel

To mount NFS through the stunnel encrypted tunnel, we run:

# Create a mount point
[root@r0 ~]# mkdir -p /data/nfs/k3svolumes

# Mount through stunnel (using localhost and NFSv4)
[root@r0 ~]# mount -t nfs4 -o port=2323 127.0.0.1:/data/nfs/k3svolumes /data/nfs/k3svolumes

# Verify mount
[root@r0 ~]# mount | grep k3svolumes
127.0.0.1:/data/nfs/k3svolumes on /data/nfs/k3svolumes 
  type nfs4 (rw,relatime,vers=4.2,rsize=131072,wsize=131072,
  namlen=255,hard,proto=tcp,port=2323,timeo=600,retrans=2,sec=sys,
  clientaddr=127.0.0.1,local_lock=none,addr=127.0.0.1)

# For persistent mount, add to /etc/fstab:
127.0.0.1:/k3svolumes /data/nfs/k3svolumes nfs4 port=2323,_netdev,soft,timeo=10,retrans=2,intr 0 0


Note: The mount uses localhost (`127.0.0.1`) because stunnel is listening locally and forwarding the encrypted traffic to the remote server.

Testing CARP Failover with mounted clients and stale file handles:

To test the failover process:

# On f0 (current MASTER) - trigger failover
paul@f0:~ % doas ifconfig re0 vhid 1 state backup

# On f1 - verify it becomes MASTER
paul@f1:~ % ifconfig re0 | grep carp
    inet 192.168.1.138 netmask 0xffffffff broadcast 192.168.1.138 vhid 1

# Check stunnel is now listening on f1
paul@f1:~ % doas sockstat -l | grep 2323
stunnel  stunnel    4567  3  tcp4   192.168.1.138:2323    *:*

# On client - verify NFS mount still works
[root@r0 ~]# ls /data/nfs/k3svolumes/
[root@r0 ~]# echo "Test after failover" > /data/nfs/k3svolumes/failover-test.txt


After a CARP failover, NFS clients may experience "Stale file handle" errors because they cached file handles from the previous server. To resolve this manually, we can run:

# Force unmount and remount
[root@r0 ~]# umount -f /data/nfs/k3svolumes
[root@r0 ~]# mount /data/nfs/k3svolumes


For the automatic recovery, we create a script:

[root@r0 ~]# cat > /usr/local/bin/check-nfs-mount.sh << 'EOF'
#!/bin/bash
# Fast NFS mount health monitor - runs every 10 seconds via systemd timer

MOUNT_POINT="/data/nfs/k3svolumes"
LOCK_FILE="/var/run/nfs-mount-check.lock"

# Use a lock file to prevent concurrent runs
if [ -f "$LOCK_FILE" ]; then
    exit 0
fi
touch "$LOCK_FILE"
trap "rm -f $LOCK_FILE" EXIT

fix_mount () {
    echo "Attempting to remount NFS mount $MOUNT_POINT"
    if mount -o remount -f "$MOUNT_POINT" 2>/dev/null; then
        echo "Remount command issued for $MOUNT_POINT"
    else
        echo "Failed to remount NFS mount $MOUNT_POINT"
    fi

    echo "Checking if $MOUNT_POINT is a mountpoint"
    if mountpoint "$MOUNT_POINT" >/dev/null 2>&1; then
        echo "$MOUNT_POINT is a valid mountpoint"
    else
        echo "$MOUNT_POINT is not a valid mountpoint, attempting mount"
        if mount "$MOUNT_POINT"; then
            echo "Successfully mounted $MOUNT_POINT"
            return
        else
            echo "Failed to mount $MOUNT_POINT"
        fi
    fi

    echo "Attempting to unmount $MOUNT_POINT"
    if umount -f "$MOUNT_POINT" 2>/dev/null; then
        echo "Successfully unmounted $MOUNT_POINT"
    else
        echo "Failed to unmount $MOUNT_POINT (it might not be mounted)"
    fi

    echo "Attempting to mount $MOUNT_POINT"
    if mount "$MOUNT_POINT"; then
        echo "NFS mount $MOUNT_POINT mounted successfully"
        return
    else
        echo "Failed to mount NFS mount $MOUNT_POINT"
    fi

    echo "Failed to fix NFS mount $MOUNT_POINT"
    exit 1
}

if ! mountpoint "$MOUNT_POINT" >/dev/null 2>&1; then
    echo "NFS mount $MOUNT_POINT not found"
    fix_mount
fi

if ! timeout 2s stat "$MOUNT_POINT" >/dev/null 2>&1; then
    echo "NFS mount $MOUNT_POINT appears to be unresponsive"
    fix_mount
fi
EOF

[root@r0 ~]# chmod +x /usr/local/bin/check-nfs-mount.sh


And we create the systemd service as follows:

[root@r0 ~]# cat > /etc/systemd/system/nfs-mount-monitor.service << 'EOF'
[Unit]
Description=NFS Mount Health Monitor
After=network-online.target

[Service]
Type=oneshot
ExecStart=/usr/local/bin/check-nfs-mount.sh
StandardOutput=journal
StandardError=journal
EOF


And we also create the systemd timer (runs every 10 seconds):

[root@r0 ~]# cat > /etc/systemd/system/nfs-mount-monitor.timer << 'EOF'
[Unit]
Description=Run NFS Mount Health Monitor every 10 seconds
Requires=nfs-mount-monitor.service

[Timer]
OnBootSec=30s
OnUnitActiveSec=10s
AccuracySec=1s

[Install]
WantedBy=timers.target
EOF


To enable and start the timer, we run:

[root@r0 ~]# systemctl daemon-reload
[root@r0 ~]# systemctl enable nfs-mount-monitor.timer
[root@r0 ~]# systemctl start nfs-mount-monitor.timer

# Check status
[root@r0 ~]# systemctl status nfs-mount-monitor.timer
● nfs-mount-monitor.timer - Run NFS Mount Health Monitor every 10 seconds
     Loaded: loaded (/etc/systemd/system/nfs-mount-monitor.timer; enabled)
     Active: active (waiting) since Sat 2025-07-06 10:00:00 EEST
    Trigger: Sat 2025-07-06 10:00:10 EEST; 8s left

# Monitor logs
[root@r0 ~]# journalctl -u nfs-mount-monitor -f


Note: Stale file handles are inherent to NFS failover because file handles are server-specific. The best approach depends on your application's tolerance for brief disruptions. Of course, all the changes made to `r0` above must also be applied to `r1` and `r2`.

Complete Failover Test

Here's a comprehensive test of the failover behaviour with all optimisations in place:

# 1. Check the initial state
paul@f0:~ % ifconfig re0 | grep carp
    carp: MASTER vhid 1 advbase 1 advskew 0
paul@f1:~ % ifconfig re0 | grep carp
    carp: BACKUP vhid 1 advbase 1 advskew 0

# 2. Create a test file from a client
[root@r0 ~]# echo "test before failover" > /data/nfs/k3svolumes/test-before.txt

# 3. Trigger failover (f0 → f1)
paul@f0:~ % doas ifconfig re0 vhid 1 state backup

# 4. Monitor client behaviour
[root@r0 ~]# ls /data/nfs/k3svolumes/
ls: cannot access '/data/nfs/k3svolumes/': Stale file handle

# 5. Check automatic recovery (within 10 seconds)
[root@r0 ~]# journalctl -u nfs-mount-monitor -f
Jul 06 10:15:32 r0 nfs-monitor[1234]: NFS mount unhealthy detected at \
  Sun Jul 6 10:15:32 EEST 2025
Jul 06 10:15:32 r0 nfs-monitor[1234]: Attempting to fix stale NFS mount at \
  Sun Jul 6 10:15:32 EEST 2025
Jul 06 10:15:33 r0 nfs-monitor[1234]: NFS mount fixed at \
  Sun Jul 6 10:15:33 EEST 2025


Failover Timeline:


0 seconds: CARP failover triggered
0-2 seconds: Clients get "Stale file handle" errors (not hanging)
3-10 seconds: Soft mounts ensure quick failure of operations
Within 10 seconds: Automatic recovery via systemd timer


Benefits of the Optimised Setup:


No hanging processes - Soft mounts fail quickly
Clean failover - Old server stops serving immediately
Fast automatic recovery - No manual intervention needed
Predictable timing - Recovery within 10 seconds with systemd timer
Better visibility - systemd journal provides detailed logs


Important Considerations:


Recent writes (within 1 minute) may not be visible after failover due to replication lag
Applications should handle brief NFS errors gracefully
For zero-downtime requirements, consider synchronous replication or distributed storage (see "Future storage explorations" section later in this blog post)


Conclusion

We've built a robust, encrypted storage system for our FreeBSD-based Kubernetes cluster that provides:


High Availability: CARP ensures the storage VIP moves automatically during failures
Data Protection: ZFS encryption protects data at rest, stunnel protects data in transit
Continuous Replication: 1-minute RPO for the data, automated via `zrepl`
Secure Access: Client certificate authentication prevents unauthorised access


Some key lessons learned are:


Stunnel vs Native NFS/TLS: While native encryption would be ideal, stunnel provides better cross-platform compatibility
Manual vs Automatic Failover: For storage systems, controlled failover often prevents more problems than it causes
Client Compatibility: Different NFS implementations behave differently - test thoroughly


Future Storage Explorations

While `zrepl` provides excellent snapshot-based replication for disaster recovery, there are other storage technologies worth exploring for the f3s project:

MinIO for S3-Compatible Object Storage

MinIO is a high-performance, S3-compatible object storage system that could complement our ZFS-based storage. Some potential use cases:


S3 API compatibility: Many modern applications expect S3-style object storage APIs. MinIO could provide this interface while using our ZFS storage as the backend.
Multi-site replication: MinIO supports active-active replication across multiple sites, which could work well with our f0/f1/f2 node setup.
Kubernetes native: MinIO has excellent Kubernetes integration with operators and CSI drivers, making it ideal for the f3s k3s environment.


MooseFS for Distributed High Availability

MooseFS is a fault-tolerant, distributed file system that could provide proper high-availability storage:


True HA: Unlike our current setup, which requires manual failover, MooseFS provides automatic failover with no single point of failure.
POSIX compliance: Applications can use MooseFS like any regular filesystem, no code changes needed.
Flexible redundancy: Configure different replication levels per directory or file, optimising storage efficiency.
FreeBSD support: MooseFS has native FreeBSD support, making it a natural fit for the f3s project.


Both technologies could run on top of our encrypted ZFS volumes, combining ZFS's data integrity and encryption features with distributed storage capabilities. This would be particularly interesting for workloads that need either S3-compatible APIs (MinIO) or transparent distributed POSIX storage (MooseFS). What about Ceph and GlusterFS? Unfortunately, there doesn't seem to be great native FreeBSD support for them. However, other alternatives also appear suitable for my use case.

Read the next post of this series:

f3s: Kubernetes with FreeBSD - Part 7: k3s and first pod deployments

Other *BSD-related posts:

2025-12-07 f3s: Kubernetes with FreeBSD - Part 8: Observability
2025-10-02 f3s: Kubernetes with FreeBSD - Part 7: k3s and first pod deployments
2025-07-14 f3s: Kubernetes with FreeBSD - Part 6: Storage (You are currently reading this)
2025-05-11 f3s: Kubernetes with FreeBSD - Part 5: WireGuard mesh network
2025-04-05 f3s: Kubernetes with FreeBSD - Part 4: Rocky Linux Bhyve VMs
2025-02-01 f3s: Kubernetes with FreeBSD - Part 3: Protecting from power cuts
2024-12-03 f3s: Kubernetes with FreeBSD - Part 2: Hardware and base installation
2024-11-17 f3s: Kubernetes with FreeBSD - Part 1: Setting the stage
2024-04-01 KISS high-availability with OpenBSD
2024-01-13 One reason why I love OpenBSD
2022-10-30 Installing DTail on OpenBSD
2022-07-30 Let's Encrypt with OpenBSD and Rex
2016-04-09 Jails and ZFS with Puppet on FreeBSD

E-Mail your comments to `paul@nospam.buetow.org`

Back to the main site

f3s: Kubernetes with FreeBSD - Part 6: Storage

Table of Contents

Introduction

Additional storage capacity

ZFS encryption keys

UFS on USB keys

Generating encryption keys

Configuring `zdata` ZFS pool encryption

Migrating Bhyve VMs to an encrypted `bhyve` ZFS volume

ZFS Replication with `zrepl`

Understanding Replication Requirements

Installing `zrepl`

Configuring `zrepl` on `f1` (sink)

Enabling and starting `zrepl` services

Monitoring replication

Verifying replication after reboot

Understanding Failover Limitations and Design Decisions

Mounting the NFS datasets

Troubleshooting: Files not appearing in replication

Configuring automatic key loading on boot

Troubleshooting: zrepl Replication Not Working

Check if zrepl Services are Running

Check zrepl Status for Errors

Fixing "No Common Snapshot" Errors

Network Connectivity Issues

Encryption Key Issues

Monitoring Ongoing Replication

CARP (Common Address Redundancy Protocol)

How CARP Works

Configuring CARP

CARP State Change Notifications

NFS Server Configuration

Setting up NFS on `f0` (Primary)

Configuring Stunnel for NFS Encryption with CARP Failover

Creating a Certificate Authority for Client Authentication

Install and Configure Stunnel on `f0`

Setting up NFS on `f1` (Standby)

CARP Control Script for Clean Failover

CARP Management Script

Automatic Failback After Reboot

Client Configuration for NFS via Stunnel

Configuring Rocky Linux Clients (`r0`, `r1`, `r2`)

NFSv4 user mapping config on Rocky

Testing NFS Mount with Stunnel

Testing CARP Failover with mounted clients and stale file handles:

Complete Failover Test

Conclusion

Future Storage Explorations

MinIO for S3-Compatible Object Storage

MooseFS for Distributed High Availability