Creating mirrored volumes

Two ways to create mirrored volumes

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 selected first 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 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. Follow the same disk selection policies that Data ONTAP follows when selecting disks for mirrored volumes. See the previous section, How Data ONTAP selects disks, for a list of disk selection policies.

See Creating a mirrored volume when creating a volume and Adding a plex to an existing unmirrored volume for information about creating mirrored volumes with disks you select.

Data ONTAP names plexes

Regardless of how a mirrored volume is created, Data ONTAP names the plexes of the mirrored volume. For more information about the plex naming convention, see Plex naming convention.

Viewing plex and disk pools

Viewing the disks in a plex or the spare disks in a disk pool is useful when adding disks to a plex or to understand which plex is using which disk pool. To view plexes and disk pools, complete the following step.

Step	Action
1	Enter one of the following commands: sysconfig -r or vol status -r

Example

In this example, the vol status -r command is used to view the disks in plexes and spare disks in disk pools:

filer2> vol status -r

Volume vol0 (online, normal) (block checksums)

  Plex /vol0/plex0 (online, normal, active)

    RAID group /vol0/plex0/rg0 (normal)

RAID Disk Device HA  SHELF BAY CHAN  Used (MB/blks) Phys (MB/blks)

------------------------------------------------------------------

parity     6.0   6    0    0   FC:A  17000/34816000 17160/35145032

data       6.2   6    0    2   FC:A  17000/34816000 17160/35145032

Volume newVol (online, mirrored) (block checksums)

  Plex /newVol/plex0 (online, normal, active)

    RAID group /newVol/plex0/rg0 (normal)

RAID Disk Device HA  SHELF BAY CHAN  Used (MB/blks) Phys (MB/blks)

------------------------------------------------------------------

parity     6.1   6    0    1   FC:A  17000/34816000 17160/35145032

data       6.3   6    0    3   FC:A  17000/34816000 17160/35145032

  Plex /newVol/plex2 (online, normal, active)

    RAID group /newVol/plex2/rg0 (normal)

RAID Disk Device HA  SHELF BAY CHAN  Used (MB/blks) Phys (MB/blks)

------------------------------------------------------------------

parity     3.17  3    2    1   FC:A  17000/34816000 17160/35145032

data       3.16  3    2    0   FC:A  17000/34816000 17160/35145032

Pool1 spare disks

RAID Disk Device HA  SHELF BAY CHAN  Used (MB/blks) Phys (MB/blks)

------------------------------------------------------------------

Spare disks for block or zoned checksum volumes

spare      3.18  3   2     2    FC:A  34000/69632000 34190/70022840

spare      3.19  3   2     3    FC:A  34000/69632000 34190/70022840

spare      3.20  3   2     4    FC:A  34000/69632000 34190/70022840

spare      3.21  3   2     5    FC:A  34000/69632000 34190/70022840

spare      3.22  3   2     6    FC:A  34000/69632000 34190/70022840

Pool0 spare disks

RAID Disk Device HA  SHELF BAY CHAN  Used (MB/blks) Phys (MB/blks)

------------------------------------------------------------------

Spare disks for block or zoned checksum volumes

spare      6.18  6   0     4    FC:A  17000/34816000 17160/35145032

spare      6.19  6   0     5    FC:A  17000/34816000 17160/35145032

spare      6.20  6   0     6    FC:A  17000/34816000 17160/35145032

spare      6.21  6   1     0    FC:A  17000/34816000 17160/35145032

spare      6.22  6   1     1    FC:A  17000/34816000 17160/35145032

For detailed information

The following sections discuss the ways you can create mirrored volumes: