Wednesday 19 Mar 2025

ZFS Pool Storage Upgrade

It's ZFS storage upgrade time! I am currently running two 4 TB hard drives, and one 2 TB hard drive in a RAIDZ1, which means my usable space is 5.45T. My pool has reached 86% capacity. You should not let ZFS get over 80% full due to performance downgrades. Let's upgrade.

I acquired another 4 TB enterprise hard drive from eBay for £50; this drive will replace the 2 TB hard drive. I used to have both WD and Seagate drives, but noticed I can get Toshiba enterprise drives at a good price second hand. I have four Toshiba drives (prior to getting this new one), with two in my back up server, one in my NAS and the one as an off-site backup.

Things to note:

• Always use the replace command to maintain redundancy should a drive fail during a resilver
• Think about the command before entering it
• Check you have the "autoexpand" option on in your pool, so that ZFS will reclaim space

I inserted the new drive into a space slot, booted the backup server. Here's the state before the upgrade:

=

zpool status

NAME    SIZE  ALLOC   FREE  CKPOINT  EXPANDSZ   FRAG    CAP  DEDUP    HEALTH  ALTROOT
rpool  5.45T  4.71T   760G     889M         -     0%    86%  1.00x    ONLINE  -

Resilver in progress

  pool: rpool
 state: ONLINE
status: One or more devices is currently being resilvered.  The pool will
	continue to function, possibly in a degraded state.
action: Wait for the resilver to complete.
  scan: resilver in progress since Wed Mar 19 07:56:32 2025
	2.29T scanned at 2.96G/s, 206G issued at 266M/s, 4.71T total
	68.5G resilvered, 4.27% done, 04:55:45 to go
config:

	NAME                                              STATE     READ WRITE CKSUM
	rpool                                             ONLINE       0     0     0
	  raidz1-0                                        ONLINE       0     0     0
	    ata-TOSHIBA_MG04ACA400E_XXXXXXXXXXXX          ONLINE       0     0     0
	    ata-TOSHIBA_MG04ACA400N_XXXXXXXXXXXX          ONLINE       0     0     0
	    replacing-2                                   ONLINE       0     0     0
	      ata-WDC_WD2002FFSX-XXXXXXXXXXXXXXXXXXXXXXX  ONLINE       0     0     0
	      ata-TOSHIBA_MG08ADA400E_XXXXXXXXXXXX        ONLINE       0     0     0  (resilvering)

errors: No known data errors

Command to resilver

zpool replace rpool ata-WDC_WD2002FFSX-XXXXXXXXXXXXXXXXXXXXXXX /dev/disk/by-id/ata-TOSHIBA_MG08ADA400E_XXXXXXXXXXXX

Following Resilver

Great, everything went well and I have now more capacity.

NAME    SIZE  ALLOC   FREE  CKPOINT  EXPANDSZ   FRAG    CAP  DEDUP    HEALTH  ALTROOT
rpool  10.9T  4.71T  6.20T        -         -     0%    43%  1.00x    ONLINE  -

  pool: rpool
 state: ONLINE
  scan: resilvered 1.58T in 03:30:28 with 0 errors on Wed Mar 19 11:27:00 2025
config:

	NAME                                            STATE     READ WRITE CKSUM
	rpool                                           ONLINE       0     0     0
	  raidz1-0                                      ONLINE       0     0     0
	    ata-TOSHIBA_MG04ACA400E_XXXXXXXXXXXX        ONLINE       0     0     0
	    ata-TOSHIBA_MG04ACA400N_XXXXXXXXXXXX        ONLINE       0     0     0
	    ata-TOSHIBA_MG08ADA400E_XXXXXXXXXXXX        ONLINE       0     0     0

errors: No known data errors

Conclusion

It is easy to replace a hard drive in a ZFS pool to increase capacity. I now have 10T to play with, at 43% capacity now. I will write back when a drive fails - let's hope it's not soon.