The size of a zpool can be increased by replacing all disks with larger ones rather than adding new disks to a pool. Useful when the disk space is running out and the server has no more actual space for additional drives. Simply detach the old HDDs - one at a time - and attach larger HDDs to the pool.
Below is an example of how to replace two disks in a mirror with two new ones. Note that if you actually have room for another disk, use
zpool replace instead. Also note that the mirror will need to be resilvered twice.
# Make sure that the autoexpand property is enabled zpool set autoexpand=yes mypool # Detach and remove the first old drive zpool detach mypool 1TB-A # Connect and attach the first new drive. Wait for resilver zpool attach 1TB-B 4TB-A # Detach and remove the second old drive zpool detach mypool 1TB-B # Connect and attach the second new drive. Wait for resilver zpool attach mypool 4TB-A 4TB-B # Export/import or reboot zpool export test zpool import test # Verify that the zpool has expanded zpool list # If the new space is in the "EXPANDSZ" column, expand each disk using 'online -e' zpool online -e mypool 4TB-A zpool online -e mypool 4TB-B