HowTo : Create Three Way Mirror Zpool

A three way mirror is useful if you are very very concerned about data integrity. Basically a three way mirror is similar to RAID1, except it mirrors it’s data across three drives instead of two drives. This effectively cuts your usable space to 1/3 of the total capacity of the drives, but it allows two drives to fail while maintaining data integrity.

To set up a three way mirror first run the format command to find the disks that you have in your system.

Format Command

Once you have run the format command, you should have a list of disks that you can select for your Zpool. Select the ones that you would like to use (we’ll use c4t5d0-c4t7d0) and issue this command :

zpool create tank mirror c4t5d0 c4t6d0 c4t7d0

Once you issue that command, it should build the zpool. Run the “zpool status” command to make sure it was created as expected.

Create Three Way Mirror

Thursday, June 3rd, 2010 RAID, ZFS

3 Comments to HowTo : Create Three Way Mirror Zpool

  • I never read but assumed that mirrors in ZFS increase read performance?

  • admin says:

    screamingservers: With some non-ZFS RAID solutions, read performance increases when doing mirroring, but I don’t think the read performance with ZFS is increased by the mirroring. ZFS uses checksumming to validate the blocks of a mirror during reads. The priority with ZFS seems to be protecting against data loss more than just simply improving performance. Anyway, this would be an interesting thing to benchmark to confirm.

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