Changing the RAID level for an aggregate

Changing the RAID group level

You can change the level of RAID protection configured for an aggregate. When you change an aggregate's RAID level, Data ONTAP reconfigures all the existing RAID groups to the new level and applies the new level to all subsequently created RAID groups in that aggregate.

Changing from RAID4 to RAID-DP protection

Before you change an aggregate's RAID protection from RAID4 to RAID-DP, you need to ensure that hot spare disks of sufficient number and size are available. During the conversion, Data ONTAP adds an additional disk to each existing RAID group from the storage system's hot spare disk pool and assigns the new disk the dParity disk function for the RAID-DP group. In addition, the aggregate's raidsize option is changed to RAID-DP as the default on this storage system. The raidsize option also controls the size of new RAID groups that might be created in the aggregate.

Changing an aggregate's RAID level

To change an existing aggregate's RAID protection from RAID4 to RAID-DP, complete the following steps.

Step	Action
1	Determine the number of RAID groups and the size of their parity disks in the aggregate in question by entering the following command. *aggr status aggr_name* -r**
2	Enter the following command to make sure that a hot spare disk exists on the storage system for each RAID group listed for the aggregate in question, and make sure that these hot spare disks match the size and checksum type of the existing parity disks in those RAID groups. aggr status -s If necessary, add hot spare disks of the appropriate number of appropriate number, size, and checksum type to the storage system. See Prerequisites for adding new disks.
3	Enter the following command: aggr options aggr_name raidtype raid_dp aggr_name is the aggregate whose RAID level (`raidtype`) you are changing. Example The following command changes the RAID level of the aggregate this aggr to RAID-DP: aggr options thisaggr raidtype raid_dp For backward compatibility, you can enter the following command: *vol options vol_name* raidtype raid_dp**

Step

Action

Determine the number of RAID groups and the size of their parity disks in the aggregate in question by entering the following command.

aggr status aggr_name -r

Enter the following command to make sure that a hot spare disk exists on the storage system for each RAID group listed for the aggregate in question, and make sure that these hot spare disks match the size and checksum type of the existing parity disks in those RAID groups.

aggr status -s

If necessary, add hot spare disks of the appropriate number of appropriate number, size, and checksum type to the storage system. See Prerequisites for adding new disks.

Enter the following command:

aggr options aggr_name raidtype raid_dp

aggr_name is the aggregate whose RAID level (raidtype) you are changing.

Example

The following command changes the RAID level of the aggregate this aggr to RAID-DP:

aggr options thisaggr raidtype raid_dp

For backward compatibility, you can enter the following command:

vol options vol_name raidtype raid_dp

Associated RAID group size changes

When you change the RAID protection level of an existing aggregate from RAID4 to RAID-DP, the following associated RAID group size changes take place:

A second parity disk (dParity) is automatically added to each existing RAID group from the hot spare disk pool, thus increasing the size of each existing RAID group by one.
If hot spare disks available on the storage system are of insufficient number or size to support the RAID level conversion, Data ONTAP issues a warning before executing the command to set the RAID level to RAID-DP (either aggr options aggr_name raidtype raid_dp or vol options vol_name raidtype raid_dp).

If you continue the operation, RAID-DP protection is implemented on the aggregate in question, but some of its RAID groups for which no second parity disk was available remain degraded. In this case, the protection offered is no improvement over RAID4, and no hot spare disks are available in case of disk failure since all were reassigned as dParity disk.
The aggregate's raidsize option, which sets the size for any new RAID groups created in this aggregate, is automatically reset to one of the following RAID-DP defaults:
- On all non-NearStore storage systems, 16
- On an R100 storage system, 12
- On an R150 storage system, 12
- On an R200 storage system, 14
- On all NetApp storage systems that support ATA disks, 14
  Note
  After the aggr options aggr_name raidtype raid_dp operation is complete, you can manually change the raidsize option through the aggr options aggr_name raidsize command. See Changing the maximum size of RAID groups.
  
  For backward compatibility, you can also use the following commands for traditional volumes:
  vol options vol_name raidtype raid_dp operation
  vol options vol_name raidsize command

Changing from RAID-DP to RAID4 protection

Changing an aggregate's RAID level

While it is possible to change an aggregate from RAID-DP to RAID4, there is a restriction, as described in the following note.

Note
You cannot change an aggregate from RAID-DP to RAID4 if the aggregate contains a RAID group larger than the maximum allowed for RAID4.

To change an existing aggregate's RAID protection from RAID-DP to RAID4, complete the following step.

Step	Action
1	Enter the following command: aggr options aggr_name raidtype raid4 aggr_name is the aggregate whose RAID level (`raidtype`) you are changing. Example The following command changes the RAID level of the aggregate thataggr to RAID4: aggr options thataggr raidtype raid4

Associated RAID group size changes

The RAID group size determines the size of any new RAID groups created in an aggregate. When you change the RAID protection of an existing aggregate from RAID-DP to RAID4, Data ONTAP automatically carries out the following associated RAID group size changes:

In each of the aggregate's existing RAID groups, the RAID-DP second parity disk (dParity) is removed and placed in the hot spare disk pool, thus reducing each RAID group's size by one parity disk.
For NearStore storage systems, Data ONTAP changes the aggregate's raidsize option to the RAID4 default sizes, as indicated on the following storage systems:
- R100 (8)
- R150 (6)
- R200 (7)
For non-NearStore storage systems, Data ONTAP changes the setting for the aggregate's raidsize option to the size of the largest RAID group in the aggregate. However, there are two exceptions:
- If the aggregate's largest RAID group is larger than the maximum RAID4 group size on non-NearStore storage systems (14), then the aggregate's raidsize option is set to 14.
- If the aggregate's largest RAID group is smaller than the default RAID4 group size on non-NearStore storage systems (8), then the aggregate's raidsize option is set to 8.
For storage systems that support ATA disks, Data ONTAP changes the setting for the aggregate's raidsize option to 7.
Note
For storage systems that support ATA disks, the restriction about not being able to change an aggregate from RAID-DP to RAID4 if the aggregate contains a RAID group larger than the maximum allowed for RAID4 also applies to traditional volumes.

After the aggr options aggr_name raidtype raid_dp operation is complete, you can manually change the raidsize option through the aggr options aggr_name raidsize command. See Changing the maximum size of RAID groups.

For backward compatibility, you can also use the following commands for traditional volumes:

vol options vol_name raidtype raid_dp
vol options vol_name raidsize

Verifying the RAID level

To verify the RAID level of an aggregate, complete the following step.

Step	Action
1	Enter the following command: aggr status aggr_name or aggr options aggr_name For backward compatibility, you can also enter the following command: `vol options` vol_name