You need to follow certain rules regarding the distribution and size of disks when adding disks to a mirrored aggregate.
- The number of disks must be even, and the disks must be equally divided between the two plexes.
- The disks for each plex must come from different disk pools.
- The disks that you add must have equivalent bytes per sector (bps) sizes.
When adding new disks to a RAID group, the utilization of the new disks depends on the RAID level used. If the storage capacity of the new disks is more than the disks already in the RAID group, the larger-capacity disks might be downsized to suit the RAID group.
- RAID-DP: Larger-capacity disks are downsized to size of parity disks.
- RAID-4: Larger-capacity disks can replace the parity disks.