Managing Plexes

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A plex is a sync-mirrored volume that contains two copies of the same file system.  You can create a mirrored volume in the following ways:

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

• You can add a plex to an existing unmirrored volume. 

Note: A mirrored volume cannot have more than two plexes.

How Data ONTAP selects disks 

Regardless of which way you create a mirrored volume, when you create a mirrored volume or add disks to a mirrored volume, Data ONTAP determines what disks to use. Data ONTAP uses the following disk selection policies when selecting disks for mirrored volumes:

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

• If there is no equivalent sized disk, Data ONTAP takes a larger capacity disk and downsizes it.

Disk selection policies if you select disks  

Data ONTAP allows you to select disks when creating mirrored volumes or adding disks to a mirrored volume. The disk selection policies that you should follow are the policies that Data ONTAP follows when selecting disks for mirrored volumes. See the Data ONTAP Storage Management Guide for more information.

Data ONTAP names plexes  

Regardless of whether Data ONTAP or you create the mirrored volume, Data ONTAP names the plexes of the mirrored volume. See the Data ONTAP Storage Management Guide for more information about the plex naming convention.