ZFS – Can one mirrored pair be a different size than another pair

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If I have a mirrored pair of 250GB drives in a pool, and I later buy two more drives and add another mirrored pair to the same pool, can that second mirrored pair be 500gb? Such that my total usable space would be 750GB?

Or do all the mirrored pairs in a pool need to be the same size?

Best Answer

Yes this is possible. The only requirement is that the mirrored pairs within the pool are the same size. ZFS does prefer to use the raw drive so ideally this means drives of the same size. But if you have a 750GB and a 500GB you can slice the 750GB to create a 500GB slice and use that slice in the pool.

This blog has some more details on this question and other questions about ZFS.

Related Solutions

ZFS: destroy and recreate mirrored zpool without losing any data. Possible

Why do you need to rebuild the pool? How much data is actually contained in the pool? That will have a greater effect on your migration strategy than anything else. If it is possible to place the data on a single disk (e.g. 1 or 2 Terabytes), I'd do that rather than risk a stripe of unmirrored disks. But again, it depends on how much data needs to move.

ZFS Pool with Different Drive Sizes

There is a better way, create a single 3 TB pool composed of two mirrors.

zpool create test mirror disk1 disk2 mirror disk3 disk4

with disk1 and disk2 being the 1TB disks and disk3 and disk4 being the 2 TB ones.

Edit:

Should you want to maximize size and do not care that much about performance or best practices, you can partition all the drives with equal size partitions (or slices) and create a 4 TB hybrid pool with a 4 vdev RAIDZ and a 2 vdev mirror.

zpool create -f test raidz d0p1 d1p1 d2p1 d3p1 mirror d0p2 d1p2

Note the "-f" option required to force the command to accept the replication level mismatch.

Best Answer

Related Solutions

ZFS: destroy and recreate mirrored zpool without losing any data. Possible

ZFS Pool with Different Drive Sizes

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