Adding disks to aggregates

Rules for adding disks to an aggregate

You can add disks of various sizes in an aggregate, using the following rules:

You can add only hot spare disks to an aggregate.
You must specify the aggregate to which you are adding the disks.
If you are using mirrored aggregates, the disks must come from the same spare disk pool.
If the added disk replaces a failed data disk, its capacity is limited to that of the failed disk.
If the added disk is not replacing a failed data disk and it is not larger than the parity disk, its full capacity (subject to rounding) is available as a data disk.
If the added disk is larger than an existing parity disk, see Adding disks larger than the parity disk.

If you want to add disks of different speeds, follow the guidelines described in the section about Disks must have the same RPM..

Checksum type rules for creating or expanding aggregates

You must use disks of the appropriate checksum type to create or expand aggregates, as described in the following rules.

You can add a BCD to a block checksum aggregate or a zoned checksum aggregate.
You cannot add a ZCD to a block checksum aggregate. For information, see How Data ONTAP enforces checksum type rules.
To use block checksums when you create a new aggregate, you must have at least the number of block checksum spare disks available that you specified in the aggr create command.

The following table shows the types of disks that you can add to an existing aggregate of each type.

Disk type	Block checksum aggregate	Zoned checksum aggregate
Block checksum	OK to add	OK to add
Zoned checksum	Not OK to add	OK to add

Hot spare disk planning for aggregates

To fully support an aggregate's RAID disk failure protection, at least one hot spare disk is required for that aggregate. As a result, the storage system should contain spare disks of sufficient number and capacity to

Support the size of the aggregate that you want to create
Serve as replacement disks should disk failure occur in any aggregate
Note
The size of the spare disks should be equal to or greater than the size of the aggregate disks that the spare disks might replace.

To avoid possible data corruption with a single disk failure, always install at least one spare disk matching the size and speed of each aggregate disk.

Adding disks larger than the parity disk

If an added disk is larger than an existing parity disk, the added disk replaces the smaller disk as the parity disk, and the smaller disk becomes a data disk. This enforces a Data ONTAP rule that the parity disk must be at least as large as the largest data disk in a RAID group.

Note
In aggregates configured with RAID-DP, the larger added disk replaces any smaller regular parity disk, but its capacity is reduced, if necessary, to avoid exceeding the capacity of the smaller-sized dParity disk.

Adding disks to an aggregate

To add new disks to an aggregate or a traditional volume, complete the following steps.

Step	Action
1	Verify that hot spare disks are available for you to add by entering the following command: aggr status -s
2	Add the disks by entering the following command: *aggr add aggr_name* [-f] [-n] {ndisks[@disk-size] \| [-d disk1 [disk2 ...] [disk1 [disk2 ...] ] }** aggr_name is the name of the aggregate to which you are adding the disks. `-f` overrides the default behavior that does not permit disks in a plex to span disk pools (only applicable if SyncMirror is licensed). This option also allows you to mix disks with different speeds. `-n` causes the command that Data ONTAP will execute to be displayed without actually executing the command. This is useful for displaying the disks that would be automatically selected prior to executing the command. ndisks is the number of disks to use. disk-size is the disk size, in gigabytes, to use. You must have at least ndisks available disks of the size you specify. `-d` specifies that the disk-name will follow. If the aggregate is mirrored, then the `-d` argument must be used twice (if you are specifying disk-names). disk-name is the disk number of a spare disk; use a space to separate disk numbers. The disk number is under the Device column in the `aggr status -s` display. Note If you want to use block checksum disks in a zoned checksum aggregate even though there are still zoned checksum hot spare disks, use the `-d` option to select the disks. Examples The following command adds four 72-GB disks to the thisaggr aggregate: aggr add thisaggr 4@72 The following command adds the disks 7.17 and 7.26 to the thisaggr aggregate: aggr add thisaggr -d 7.17 7.26

Step

Action

Verify that hot spare disks are available for you to add by entering the following command:

aggr status -s

Add the disks by entering the following command:

aggr add aggr_name [-f] [-n] {ndisks[@disk-size] | [-d 
disk1 [disk2 ...] [disk1 [disk2 ...] ] }

aggr_name is the name of the aggregate to which you are adding the disks.

-f overrides the default behavior that does not permit disks in a plex to span disk pools (only applicable if SyncMirror is licensed). This option also allows you to mix disks with different speeds.

-n causes the command that Data ONTAP will execute to be displayed without actually executing the command. This is useful for displaying the disks that would be automatically selected prior to executing the command.

ndisks is the number of disks to use.

disk-size is the disk size, in gigabytes, to use. You must have at least ndisks available disks of the size you specify.

-d specifies that the disk-name will follow. If the aggregate is mirrored, then the -d argument must be used twice (if you are specifying disk-names).

disk-name is the disk number of a spare disk; use a space to separate disk numbers. The disk number is under the Device column in the aggr status -s display.

Note
If you want to use block checksum disks in a zoned checksum aggregate even though there are still zoned checksum hot spare disks, use the -d option to select the disks.

Examples

The following command adds four 72-GB disks to the thisaggr aggregate:

aggr add thisaggr 4@72

The following command adds the disks 7.17 and 7.26 to the thisaggr aggregate:

aggr add thisaggr -d 7.17 7.26

Adding disks to a specific RAID group in an aggregate

If an aggregate has more than one RAID group, you can specify the RAID group to which you are adding disks. To add disks to a specific RAID group of an aggregate, complete the following step.

Step	Action
1	Enter the following command: aggr add aggr_name -g raidgroup ndisks[@disk-size] \| -d disk-name... raidgroup is a RAID group in the aggregate specified by aggr_name Example The following command adds two disks to RAID group 0 of the vol0 volume: aggr add aggr0 -g rg0 2

The number of disks you can add to a specific RAID group is limited by the raidsize setting of the aggregate to which that group belongs. For more information, see Chapter 4, Changing the size of existing RAID groups

Forcibly adding disks to aggregates

If you try to add disks to an aggregate (or traditional volume) under the following situations, the operation will fail:

The disks specified in the aggr add (or vol add) command would cause the disks on a mirrored aggregate to consist of disks from two spare pools.
The disks specified in the aggr add (or vol add) command have a different speed in revolutions per minute (RPM) than that of existing disks in the aggregate.

If you add disks to an aggregate (or traditional volume) under the following situation, the operation will prompt you for confirmation, and then succeed or abort, depending on your response.

The disks specified in the aggr add command would add disks to a RAID group other than the last RAID group, thereby making it impossible for the file system to revert to an earlier version than Data ONTAP 6.2.

To force Data ONTAP to add disks in these situations, complete the following step.

Step	Action
1	Enter the following command: aggr add aggr-name -f [-g raidgroup] -d disk-name... Note You must use the `-g` raidgroup option to specify a RAID group other than the last RAID group in the aggregate.

Displaying disk space usage on an aggregate

You use the aggr show_space command to display how much disk space FlexVol volumes use in an aggregate. The command shows the following categories of information. If you specify the name of an aggregate, the command only displays information about that aggregate. Otherwise, the command displays information about all of the aggregates in the storage system.

WAFL reserve--the amount of space used to store the metadata that Data ONTAP uses to maintain the volume.
Snapshot copy reserve--the amount of space reserved for aggregate Snapshot copies.
Usable space--the amount of total usable space (total disk space less the amount of space reserved for WAFL metadata and Snapshot copies).
Allocated space--the amount of space that was reserved for the volume when the aggregate was created, and the space used by non-reserved data.
For guaranteed volumes, this is the same amount of space as the size of the volume, since no data is unreserved.

For non-guaranteed volumes, this is the same amount of space as the used space, since all of the data is unreserved.
Used space--the amount of space that occupies disk blocks. It includes the metadata required to maintain the FlexVol volume. It can be greater than the Allocated value.
Note
This value is not the same as the value displayed for "used space" by the df command.
Available space--the amount of free space in the aggregate. You can also use the df command to display the amount of available space.
Total disk space--the amount of total disk space available to the aggregate

All of the values are displayed in 1024-byte blocks, unless you specify one of the following sizing options:

-h displays the output of the values in the appropriate size, automatically scaled by Data ONTAP
-k displays the output in kilobytes
-m displays the output in megabytes
-g displays the output in gigabytes
-t displays the output in terabytes

To display the disk usage of an aggregate, complete the following step.

Step	Action
1	Enter the following command: `aggr show_space` aggr_name Example aggr show_space -h aggr1 Aggregate `aggr1' Volume Reserved Used Guarantee vol1 100MB 80MB volume vol2 50MB 40MB volume vol3 21MB 21MB none Aggregate Reserved Used Avail Total space 171MB 142MB 83MB Snap reserve 13MB 2788KB 10MB WAFL reserve 30MB 1476KB 28MB

Step

Action

Enter the following command:

aggr show_space aggr_name

Example

aggr show_space -h aggr1

Aggregate `aggr1'

Volume            Reserved          Used     Guarantee

vol1               100MB            80MB        volume

vol2                50MB            40MB        volume

vol3                21MB            21MB          none

Aggregate         Reserved          Used         Avail

Total space          171MB         142MB          83MB

Snap reserve          13MB        2788KB          10MB

WAFL reserve          30MB        1476KB          28MB

After adding disks for LUNs, you run reallocation jobs

After you add disks to an aggregate, run a full reallocation job on each FlexVol volume contained in that aggregate. For information on how to perform this task, see your Block Access Management Guide.