Specifying the size of RAID groups

About RAID group size

You can specify a RAID group size. When a RAID group reaches the specified size, a new RAID group is created. The default size of a RAID group (including the parity disk) is 8 disks. You can also specify the size of RAID groups for a volume when you create the volume.

Maximum RAID group sizes

You can change the size of RAID groups to be created. The maximum RAID group you can create manually has 28 disks. The maximum RAID group size is 52 disks. RAID groups larger than 28 disks can be created only during conversions from older versions of Data ONTAP, Data ONTAP 4.X or earlier, that support only one RAID group.

Using larger versus smaller RAID groups

The advantages and disadvantages of using large versus small RAID groups are shown in the following table.

Factor affected	Large RAID groups	Small RAID groups
Disk reconstruction time if a disk fails	Longer	Shorter
Risk of data loss due to multiple-disk failures	Increased	Reduced
Parity disks required	Fewer	More
Data disks available	More	Fewer

Note
The risk of data loss due to multiple-disk failures is lessened if you use mirrored volumes.

Specifying the RAID group size at volume creation

To specify the RAID group size for a volume when you create it, complete the following step.

Step	Action
1	When you enter the `vol create` command, use the `-r` raid-group-size option. raid-group-size is the RAID group size you want. Example The following command creates the volume newvol with a RAID group size of 16 disks and consisting of 10 36-GB disks: vol create newvol -r 16 10@36

Changing the RAID group size

You can change the size of the most recently created RAID group. The new RAID group size applies to subsequently created RAID groups in a volume.

To change the RAID group size for an existing volume, complete the following step.

Step	Action
1	Enter the following command: vol options vol-name raidsize size vol-name is the volume whose RAID group size you are changing. size is the number of disks you want in the RAID group. Example The following command changes the RAID group size of the thisvol volume to 16 disks: vol options thisvol raidsize 16

Step

Action

Enter the following command:

vol options vol-name raidsize size

vol-name is the volume whose RAID group size you are changing.

size is the number of disks you want in the RAID group.

Example

The following command changes the RAID group size of the thisvol volume to 16 disks:

vol options thisvol raidsize 16

See Adding new disks to a RAID group and Forcibly adding disks to volumes for information about adding disks to RAID groups.