Managing Plexes

The SyncMirror software creates aggregates that consist of two plexes, providing a higher level of data consistency through RAID-level mirroring. The two plexes are simultaneously updated; therefore, the plexes are always identical.

You can create a mirrored aggregate in the following ways:

• You can create a new aggregate that has two plexes. 

• You can add a plex to an existing, unmirrored aggregate.

An aggregate cannot have more than two plexes.

Note: Data ONTAP names the plexes of the mirrored aggregate. See the Data ONTAP Storage Management Guide for more information about the plex naming convention.

How Data ONTAP selects disks 

Regardless of how you create a mirrored aggregate, Data ONTAP determines which disks to use. Data ONTAP uses the following disk-selection policies when selecting disks for mirrored aggregates:

• Disks selected for each plex must come from different disk pools. 

• The number of disks selected for one plex must equal the number of disks selected for the other plex. 

• Disks are first selected on the basis of equivalent bytes per sector (bps) size, then on the basis of the size of the disk. 

• If there is no equivalent-sized disk, Data ONTAP selects a larger-capacity disk and uses only part of the disk.

Disk selection policies if you select disks  

Data ONTAP enables you to select disks when creating or adding disks to a mirrored aggregate. You should follow the same disk-selection policies that Data ONTAP follows when selecting disks for mirrored aggregates. See the Data ONTAP Storage Management Guide for more information.