Grow ZFS mirror

Question

I have a ZFS pool with 6 disks in a RAID 10 configuration.

I would like to upgrade the drives in one of the mirrors, from 1TB to 3TB drives. I have all the drives installed in the system.

I would prefer not to do it by replacing one drive, resilver, repeat. Is there a way to perform all of my reads from existing mirror, keeping all the wear on the drives I am removing?

root@e7-4860:~# zpool status
  pool: stuffpoll
 state: ONLINE
  scan: scrub repaired 0 in 6h50m with 0 errors on Sun Dec 10 07:14:34 2017
config:

    NAME                                               STATE     READ WRITE CKSUM
    stuffpoll                                          ONLINE       0     0     0
      mirror-0                                         ONLINE       0     0     0
        ata-HGST_HTS721010A9E630_JR10004M0LGN6E-part1  ONLINE       0     0     0
        ata-HGST_HTS721010A9E630_JR10004M0M17TE-part1  ONLINE       0     0     0
      mirror-1                                         ONLINE       0     0     0
        ata-HGST_HTS541010A9E680_JA1000102MG9UR-part1  ONLINE       0     0     0
        ata-HGST_HTS541010A9E680_JA1009C03158BP-part1  ONLINE       0     0     0
      mirror-2                                         ONLINE       0     0     0
        ata-HGST_HTS721010A9E630_JR100X6P2TJKVE        ONLINE       0     0     0
        ata-HGST_HTS721010A9E630_JR100Y4M01200M        ONLINE       0     0     0

errors: No known data errors


root@e7-4860:~# zpool list
NAME        SIZE  ALLOC   FREE  EXPANDSZ   FRAG    CAP  DEDUP  HEALTH  ALTROOT
stuffpoll  2.72T  2.47T   254G         -    48%    90%  1.00x  ONLINE  -


root@e7-4860:~# ls /dev/disk/by-id/ -1
ata-CT240BX200SSD1_1613F0194817
ata-CT240BX200SSD1_1613F0194817-part1
ata-HGST_HTS541010A9E680_JA1000102MG9UR
ata-HGST_HTS541010A9E680_JA1000102MG9UR-part1
ata-HGST_HTS541010A9E680_JA1000102MG9UR-part9
ata-HGST_HTS541010A9E680_JA1009C03158BP
ata-HGST_HTS541010A9E680_JA1009C03158BP-part1
ata-HGST_HTS541010A9E680_JA1009C03158BP-part9
ata-HGST_HTS721010A9E630_JR10004M0LGN6E
ata-HGST_HTS721010A9E630_JR10004M0LGN6E-part1
ata-HGST_HTS721010A9E630_JR10004M0LGN6E-part9
ata-HGST_HTS721010A9E630_JR10004M0M17TE
ata-HGST_HTS721010A9E630_JR10004M0M17TE-part1
ata-HGST_HTS721010A9E630_JR10004M0M17TE-part9
ata-HGST_HTS721010A9E630_JR100X6P2TJKVE
ata-HGST_HTS721010A9E630_JR100X6P2TJKVE-part1
ata-HGST_HTS721010A9E630_JR100X6P2TJKVE-part9
ata-HGST_HTS721010A9E630_JR100Y4M01200M
ata-HGST_HTS721010A9E630_JR100Y4M01200M-part1
ata-HGST_HTS721010A9E630_JR100Y4M01200M-part9
scsi-35000c50055fb009b
scsi-35000c50055fb395f

I would like to ultimately replace the drives in mirror-1 with scsi-35000c50055fb009b and scsi-35000c50055fb395f

Answer 1

If you want to manually expand the volume all you have to do is bring it online with the -e option.

zpool online -e stuffpoll

You can also toggle the autoexpand option to have it happen automatically.

zpool set autoexpand=on stuffpoll

So lets say you are adding new drives to mirror-2 so you can expand that. You need to attach the new drives, using the one of the existing device names as the target. You can add both new devices to a mirror before removing the old devices.

# zpool attach pool existing_vdev_member new_device
zpool attach stuffpoll ata-HGST_HTS721010A9E630_JR100X6P2TJKVE new_dev1
zpool attach stuffpoll ata-HGST_HTS721010A9E630_JR100X6P2TJKVE new_dev2

After the sync of the new devices are complete you can remove the old devices.

zpool detach stuffpoll ata-HGST_HTS721010A9E630_JR100X6P2TJKVE
zpool detach stuffpoll ata-HGST_HTS721010A9E630_JR100Y4M01200M

Man zpool

zpool attach [-f] pool device new_device

Attaches new_device to an existing zpool device. The existing device
cannot be part of a raidz configuration. If device is not currently
part of a mirrored configuration, device automatically transforms
into a two-way mirror of device and new_device.  If device is part of
a two-way mirror, attaching new_device creates a three-way mirror,
and so on. In either case, new_device begins to resilver immediately.
...

zpool detach pool device

Detaches device from a mirror.  The operation is refused if there are
no other valid replicas of the data.  If device may be re-added to
the pool later on then consider the zpool offline command instead.
...

zpool online [-e] pool device ...

Brings the specified physical device online.
-e  Expand the device to use all available space. If the device
    is part of a mirror or raidz then all devices must be
    expanded before the new space will become available to the
    pool.

Links

• https://www.freebsd.org/cgi/man.cgi?zpool(8)
• http://www.c0t0d0s0.org/archives/6224-You-dont-need-zfs-resize-...-and-a-workaround-when-you-need-one-;.html

Also, I like to remind people. Verify your backups/restores first. There is always a chance something bad will happen. Also consider building a zfs pool on a test machine/VM and practice your commands ahead of time.