Hey folks this is a long one so thanks in advance!!! This is the first time I’ve ever done an expansion like this and so I’ve been talking with some friends and throwing stuff at multiple AI’s to get a guide for my planned process. I believe I’m at the final version and would love some review for anyone that can take the time to point out anything I missed or any sneaky errors that could cause me problems.
TrueNAS 4→8 Drive RAIDZ2 Migration Guide (v3.3)
Goal: Expand from 4-drive RAIDZ2 to 8-drive RAIDZ2
Method: ZFS → ZFS send/receive
Data Integrity: Bit-perfect, resumable, metadata-safe
Risk Level: Very Low (operator error is the only real risk)
THE GOLDEN RULES (READ ONCE)
NO WEB SHELL — use SSH only. Browser tabs kill transfers.
USE TMUX for everything long-running.
NEVER DELETE THE SOURCE until verification passes.
NO EXTRA SCRUBS ON BACKUP — they add time, not certainty.
USB DRIVE MUST STAY AWAKE — heartbeat required.
PHASE 0 — Pre-Flight & SSH Setup
Connect via SSH
ssh TrueNas @192.168.1.xxx
Start tmux
tmux
Detach: Ctrl+B, then D
Reattach: tmux attach
Confirm All Drives Are Seen
lsblk
SMART Check New Drives (Recommended)
sudo smartctl -t long /dev/sdX
Wait for completion before migrating.
PHASE 1 — Documentation & Service Shutdown
Snapshot Current Config (GUI)
Screenshot SMB/NFS shares
Screenshot Apps configuration
Capture Pool Metadata
sudo mkdir -p /root/migration_docs
sudo zfs get -r all tank > /root/migration_docs/tank_properties.txt
sudo zfs list -r -o name,mountpoint,quota tank > /root/migration_docs/tank_structure.txt
Stop All Writes
Stop all Apps
Disable SMB / NFS
Verify no open files:
sudo smbstatus
PHASE 2 — ZFS Backup to USB (Authoritative Copy)
Identify USB Disk by ID
ls -l /dev/disk/by-id/ | grep usb
Create Backup Pool
sudo zpool create -m none backup_pool /dev/disk/by-id/usb-YOUR_ID
Snapshot & Protect
sudo zfs snapshot -r tank@migration_backup
sudo zfs hold -r keep tank@migration_backup
Start the Transfer (INSIDE TMUX)
sudo zfs send -R -L -v tank@migration_backup | sudo zfs receive -s -F backup_pool/tank
USB HEARTBEAT (BEST OPTION)
Why this one:
Zero filesystem writes
Keeps USB link active
No metadata churn
Safe for long transfers
Open a Second tmux Pane
Ctrl+B, then "
Run:
zpool iostat -v backup_pool 60
This continuously polls the pool every 60 seconds and prevents WD Elements from sleeping.
This is the best option.
No touch, no cron, no filesystem spam.
Detach tmux and walk away.
IF THE BACKUP INTERRUPTS
Check for Resume Token
zfs get -H -o value receive_resume_token backup_pool/tank
If token exists:
sudo zfs send -t TOKEN | sudo zfs receive -s -F backup_pool/tank
If no token:
sudo zfs destroy -r backup_pool/tank
Restart Phase 2.
PHASE 3 — Verification (THIS IS YOUR CONFIDENCE)
Dataset Count Match
zfs list -r -o name tank | wc -l
zfs list -r -o name backup_pool/tank | wc -l
Must match exactly.
Bit-Perfect Check (THE IMPORTANT ONE)
sudo zfs diff tank@migration_backup backup_pool/tank@migration_backup
No output = perfect copy
Any output = stop and investigate
Mount & Spot-Check
sudo zfs set mountpoint=/mnt/backup backup_pool/tank
ls -la /mnt/backup/media/movies
sudo zfs set mountpoint=none backup_pool/tank
PHASE 4 — Destroy & Rebuild Pool
Destroy Old Pool (GUI)
Storage → tank → Export/Disconnect
Check Destroy data
Remove Stale Mount
sudo rmdir /mnt/tank
Create New Pool (GUI)
Name: tank
Layout: RAIDZ2 (8 drives)
Sector Size: 4K (ashift=12)
Verify Alignment
sudo zdb -C tank | grep ashift
Must be ashift=12
PHASE 5 — Restore to New Pool
Start tmux
tmux
Restore Command
sudo zfs send -R -L -v backup_pool/tank@migration_backup | sudo zfs receive -F -d tank
Why -d: prevents tank/tank/… nesting.
IF RESTORE FAILS MID-WAY
sudo zfs destroy -r tank@%recv
Then re-run the restore command.
PHASE 6 — Final Validation
Check Dataset Layout
zfs list -r tank
Ensure:
No tank/tank
Correct mountpoints
Scrub the New Pool (ONLY ONE SCRUB)
sudo zpool scrub tank
This validates all 8 drives post-restore.
Re-Enable Services
Turn SMB/NFS back on
Start Apps
Confirm permissions (they should be identical)
PHASE 7 — Cleanup (DO NOT RUSH)
Wait 7 Days
Keep the USB backup untouched.
Then:
sudo zfs release -r keep tank@migration_backup
sudo zfs destroy -r tank@migration_backup
sudo zpool export backup_pool
Unplug USB.
