Moving volumes between aggregates - FSx for ONTAP
Phases of moving a volumeStarting volume movesMonitoring volume movesMaintaining balanced FlexGroup volumesThrottling volume moves
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Moving volumes between aggregates

When you add high-availability (HA) pairs to your file system, you need to rebalance the existing data by moving volumes to the new aggregates. To move a volume between aggregates, you can use the volume move command in the ONTAP CLI.

Before using the volume move command, consider the following points:

  • Using the volume move command can impact performance because it consumes network and disk resources on your file system. Therefore, we recommend moving volumes between aggregates during periods of low activity. Alternatively, you can reduce the network throughput utilization and disk throughput utilization on your file system to no more than 50% while moving volumes.

  • To reduce the performance impact on your file system, we recommend moving a single volume between two HA pairs and aggregates at a time. For example, if your file system has four HA pairs, we recommend moving two volumes at a time (assuming the volume moves are not from or toward the same HA pairs). ONTAP supports moving up to eight volumes on each HA pair at a time, but more simultaneous volume moves will reduce the performance of both client I/O and any in-progress volume moves.

  • Any data stored on the SSD tier on the impacted volume is physically moved to a different set of disks on a different file server. This operation occurs in the background and takes time. The rate of time that the transfer takes depends on your file system's throughput capacity and the amount of activity on your file system. However, the volume move can be throttled. For more information, see Throttling volume moves.

  • Any data stored on the capacity tier is not physically moved because the HA pairs share the same capacity pool storage. As a result, moving volumes with most of their data tiered will be faster. Keep in mind that file metadata is always stored on the SSD tier. For more information, see Volume data tiering.

Phases of moving a volume

There are two phases in a volume move operation: the replication phase and the cutover phase. During the replication phase, existing data is replicated to the volume's new aggregate. During the cutover phase, ONTAP attempts a final rapid transfer to the volume's new aggregate. This includes transferring any data that has been written during the transfer phase and redirecting new traffic to the volume's new aggregate. By default, the cutover window is 30 seconds and halts all I/O to your volume. If ONTAP can't perform all of these steps during the cutover window, it will fail. By default, ONTAP will try to cut over three times consecutively. If all three consecutive attempts fail, then ONTAP will retry once an hour until it succeeds. You can reduce the load on your file system to ensure that the cutover phase is successful by reducing or pausing I/O traffic to the volume before the cutover phase begins.

Starting volume moves

To start a volume move

  1. SSH into your ONTAP file system. For more information, see Using the NetApp ONTAP CLI.

    ssh fsxadmin@file-system-management-endpoint-ip-address

  2. Run the volume move start ONTAP CLI command. Replace the following values:

    • vserver_name with the name of the SVM hosting the volume that you're moving.

    • volume_name with the name of the volume's constituent (for example, vol1__0001).

    • aggregate_name with the name of the destination aggregate for the volume.

    • -enforce-network-throttling to throttle the volume move's total throughput. This is optional. 

    ::> volume move start -vserver svm_name -volume volume_name -destination aggregate_name -foreground false
[Job 1] Job is queued: Move "vol1__0001" in Vserver "svm01" to aggregate "aggr1". Use the "volume move show -vserver svm01 -volume vol1__0001" command to view the status of this operation.
Important

Moving volumes consumes network and disk resources for the source and destination file servers. Therefore, your workload's performance can be impacted by any volume moves that are in progress. Additionally, your I/O traffic to the volume will be temporarily paused during the cutover phase of the volume move.

Monitoring volume moves

To monitor a volume move

  • To check the status of the volume move operation, use the volume move show ONTAP CLI command.

    ::> volume move show -vserver svm_name -volume volume_name 

Vserver Name: svm01
Volume Name: vol1__0001
Actual Completion Time: -
Bytes Remaining: 1.00TB
Specified Action For Cutover: retry_on_failure
Specified Cutover Time Window: 30
Destination Aggregate: aggr2
Destination Node: FsxId01234567890abcdef-03
Detailed Status: Transferring data: 12.23GB sent.
Percentage Complete: 1%
Move Phase: replicating
Prior Issues Encountered: -
Estimated Remaining Duration: 00:40:25
Replication Throughput: 434.3MB/s
Duration of Move: 00:00:27
Source Aggregate: aggr2
Source Node: FsxId01234567890abcdef-01
Move State: healthy

    The command output shows the estimated time to complete the move. When it's finished, the Move phase will show the completed status.

Maintaining balanced FlexGroup volumes

In order for your workload to perform optimally, your FlexGroup volumes should span all aggregates and have an even number of constituent volumes per aggregate. We recommend having eight constituents per aggregate. Consider the following scenarios when rebalancing FlexGroup volumes:

  • Moving FlexGroup constituents among existing aggregates: If you move a FlexGroup's constituent volume to another aggregate of an otherwise balanced FlexGroup, you should then move another constituent that's less utilized to the original aggregate. This ensures that your FlexGroup has an even number of constituents per aggregate.

    Moving FlexGroup constituents into new aggregates after adding HA pairs: If you move a FlexGroup's constituent volumes to new aggregates after adding HA pairs, then you should expand the FlexGroup with additional constituents on the aggregates that lost constituents. This ensures that your FlexGroup has an even number of constituents per aggregate. For more information, see Expanding FlexGroup volumes.

Throttling volume moves

If you want to limit the bandwidth of a volume move on your file system, you can add the -enforce-network-throttling option at the beginning of the operation.

Note

Using this option affects incoming SnapMirror replication data transfers for the file system. Keep track of how you configure your file system's replication options because you can't view them after setting them.

To throttle a volume move

  1. The throttle uses the global replication throttle. To set the global replication throttle, use the following command in the ONTAP CLI.

    ::> options -option-name replication.throttle.enable on

  2. Specify the maximum total bandwidth that can be used by replication, replacing the following option:

    • kbs_throttle with the maximum desired throughput to use for any replication (including SnapMirror and volume moves), in Kilobytes per second.

    ::> options -option-name replication.throttle.incoming.max_kbs kbs_throttle 
::> options -option-name replication.throttle.outgoing.max_kbs kbs_throttle