These days, one of the drives on one of my machines started developing bad habits of reallocating blocks which is an early sign that drive might go bad. To prevent such misfortune I decided to replace it with a new one.
Once the old drive was yanked out and new one was put into the machine (there are other ways, but I was forced to do it this way) it was only left to partition the new drive and add it to appropriate places.
First step was to check how the remaining drive was partitioned:
root@ncc-1701:~ # gpart show ada0
=> 40 5860533088 ada0 GPT (2.7T)
40 1024 1 freebsd-boot (512K)
1064 984 - free - (492K)
2048 8388608 2 freebsd-swap (4.0G)
8390656 5852141568 3 freebsd-zfs (2.7T)
5860532224 904 - free - (452K)
Situation here is pretty much self-explanatory. The partition /dev/ada1p3 is one of the providers in ZFS mirror (mind that this is situation after everything was done and is here just for illustrative purposes):
root@ncc-1701:~ # zpool list -v
NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
zroot 2.72T 132G 2.59T - 6% 4% 1.00x ONLINE -
mirror 2.72T 132G 2.59T - 6% 4%
ada0p3 - - - - - -
ada1p3 - - - - - -
OK, now that we know where goes where, let’s partition the new ada1 drive the same way as the ada0 is partitioned:
Create new partition table:
root@ncc-1701:~ # gpart create -s gpt ada1
ada1 created
Create boot partition:
root@ncc-1701:~ # gpart add -b 40 -s 1024 -t freebsd-boot ada1
ada1p1 added
Switch -b here, specifies LBA at which partition starts and -s specifies the size.
Install bootcode to the drive since it is part of a mirror from which server boots:
root@ncc-1701:~ # gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 ada1
partcode written to ada1p1
bootcode written to ada1
Create swap partition:
root@ncc-1701:~ # gpart add -b 2048 -s 8388608 -t freebsd-swap -l swap ada1
ada1p2 added
Create ZFS storage provider partition:
root@ncc-1701:~ # gpart add -b 8390656 -s 5852141568 -t freebsd-zfs -l disk2 ada1
ada1p3 added
Partition is used as a provider, but this can be any GEOM device. This is just the way FreeBSD does things on default install.
With this done, I got the following situation:
root@ncc-1701:~ # gpart show ada1
=> 40 5860533088 ada1 GPT (2.7T)
40 1024 1 freebsd-boot (512K)
1064 984 - free - (492K)
2048 8388608 2 freebsd-swap (4.0G)
8390656 5852141568 3 freebsd-zfs (2.7T)
5860532224 904 - free - (452K)
Exactly like on ada0 :-)
Now all is left to do is to attach the drive back to the ZFS pool again:
root@ncc-1701:~ # zpool attach zroot ada0p3 ada1p3
To explain this further; ada0p3 was already part of a ZFS mirror VDEV but was “missing a pair”, here, we simply attached ada1p3 to it, making it a healthy mirror again (once resilver process is complete).
Monitoring resilver process can be done this way:
root@ncc-1701:~ # zpool status -v
pool: zroot
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 Tue Dec 19 18:50:48 2017
71.6M scanned out of 132G at 2.11M/s, 17h46m to go
71.3M resilvered, 0.05% done
config:
NAME STATE READ WRITE CKSUM
zroot ONLINE 0 0 0
mirror-0 ONLINE 0 0 0
ada0p3 ONLINE 0 0 0
ada1p3 ONLINE 0 0 0 (resilvering)
errors: No known data errors
That may take some time, depending on how much data you have :-)
You may notice that there is some random device in that mirror, called 15380924691328095690 or something similar. That is basically identifier of the missing device that was yanked out. In previous step I used zpool attach command to add the device since I’ve already performed:
zpool detach zroot 15380924691328095690
If I didn’t do that, to replace the drive, I would need to use:
zpool replace zroot 15380924691328095690 ada1p3
At this point, after filtering through all the mess I put here, you might wonder; “what about that swap partition”?
- Nothing, I simply ran
swapon -aand it was used again as the swap since my/etc/fstabalready had it specified by the name (ada1p2).