On my NAS server, I want to upgrade from two 6TB drives to two 16TB drives. I’m currently using ZFS, but I’m not really sure how to do the expansion. After some searching, I find this blog post.

According to the blog post, this should be sufficient for upgrading the pool:

zpool set autoexpand=on <pool>
zpool replace <pool> <old disk> <new disk>

So in my case, I did:

zpool set autoexpand=on data
zpool replace data ata-ST6000NM019B-2TG103_WX00D8PA /dev/disk/by-id/ata-ST16000NM001G-2KK103_ZL2KFS22
zpool replace data ata-ST6000NM019B-2TG103_WX00DFDG /dev/disk/by-id/ata-ST16000NM001G-2KK103_ZL2L1YQG

This automatically started the resilvering process. Rebooting the computer while this process was happening didn’t cause the operation to fail, but it did appear to lose some progress. After the resilvering, the pool was now 14.4 TB big according to zfs list storage. While I was expecting the size to be lower, I’m not sure exactly why the size was 1.6 TB lower than expected.

The blog post I read also mentioned that if I forgot to set autoexpand before replacing, I could fix the issue by doing online -e for each drive:

zpool online -e <pool> <disk>