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Requirements when using mirrored aggregates

If you want to use mirrored aggregates to retain two copies of data, you can either create a new aggregate with two mirrored plexes, or, if you have an aggregate already, add a plex to the existing aggregate (a mirrored aggregate can have only two plexes).

The rules for the selection of disks or array LUNs for use as mirrored aggregates are as follows:
  • Disks or array LUNs selected for each plex must be in different pools.
  • The same number of disks or array LUNs must be in both plexes.
  • Disks are selected first on the basis of equivalent bytes per sector (bps), and then on the basis of the size of the disk.
  • If there is no equivalent-sized disk, Data ONTAP uses a larger-capacity disk and limits the size to make it identically sized.
  • Data ONTAP names the plexes of the mirrored aggregate.

When creating an aggregate, Data ONTAP selects disks from the pool that has the most available disks. You can override this selection policy by specifying the disks to use.

Note: This is true only for clusters that are not MetroCluster clusters.