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vfiler run * snapmirror status

How FlexClone volumes impact SnapMirror

You can create FlexClone volumes from SnapMirror source or destination volumes. However, you should understand the behavior of the resulting FlexClone volume before creating it.

FlexClone volumes create a nearly instantaneous replica of a volume within the same aggregate. For information about FlexClone volumes, see the Data ONTAP Storage Management Guide for 7-Mode.

The following two sections list the key differences between cloning volumes that use qtree SnapMirror and cloning volumes that use volume SnapMirror.

Volume SnapMirror and FlexClone

• When a clone is created on a volume SnapMirror destination system, Data ONTAP locks the Snapshot copy that the clone is based on. To protect the clone, Data ONTAP does not allow you to delete this Snapshot copy. Data ONTAP also puts a soft lock on the corresponding Snapshot copy on the SnapMirror source system.

• Although Data ONTAP will not delete this Snapshot copy that is the source of a clone, you can manually delete this Snapshot copy on the SnapMirror source volume. If you delete the Snapshot copy on the source volume, the next SnapMirror update will fail because it attempts to delete the corresponding Snapshot on the destination volume. All SnapMirror updates to the destination volume continue to fail until the clone is destroyed or split.

Attention: Delete Snapshot copies carefully when SnapMirror and FlexClone are involved.

• Always create a clone from the most recent Snapshot copy in the SnapMirror destination, because that copy is guaranteed to exist in the source volume.

If a FlexClone volume is created from a Snapshot copy in the destination volume that is not the most recent copy, and that Snapshot copy no longer exists on the source volume, all the SnapMirror updates to the destination volume will fail until the clone is destroyed or split. This happens because SnapMirror update attempts to delete the snapshot copy on the destination system, which is locked due to the creation of a FlexClone volume.

Qtree SnapMirror and FlexClone

• Qtree SnapMirror does not maintain the same Snapshot copies of the volume on the source and destination systems. Because of this characteristic, a FlexClone volume created from a Snapshot copy on the qtree SnapMirror destination does not lock that Snapshot copy on the source volume.

• Accordingly, deleting that Snapshot copy on the source volume has no impact on the replication or the destination volume. Therefore, the advantage of qtree SnapMirror is that a FlexClone volume can live for a long time on the SnapMirror destination system without space implications on the source system.

• If a Snapshot copy is not specified when creating a FlexClone volume on the qtree SnapMirror destination volume, the ^{vol clone} command creates a new Snapshot copy on that volume.

• If a FlexClone volume is created using the qtree SnapMirror baseline Snapshot copy, the qtree in the FlexClone volume will be writable.

• If a FlexClone volume is created on the qtree SnapMirror destination volume without specifying a backing Snapshot copy for the clone creation, a separate SnapMirror relationship appears in the snapmirror status command output.

Setting up a SnapMirror relationship between two FlexClone volumes

The SnapMirror relationship between two FlexClone volumes that have the common base snapshot helps you to achieve a SnapMirror relationship without transferring the common snapshot data again to the destination system. Both the FlexClone volumes should be created from the SnapMirror source and the corresponding SnapMirror destination volumes with a common base snapshot.

About this task

Setting up a SnapMirror relationship between the two FlexClone volumes does not consume any extra space on the parent aggregate for shared Snapshot copies. In this way, you save disk space and network resources. If you delete any of the inherited Snapshot copies from the parent system or transfer new data from the SnapMirror source clone to the SnapMirror destination clone, additional disk space is consumed.

Step

1. Establish the SnapMirror relationship between the two FlexClone volumes by entering the following command on the destination FlexClone volume:

snapmirror resync -S source:sourcevol destination:destinationvol

Note: The snapmirror resync command cannot establish the SnapMirror relationship if the background scanners are still processing the parent destination volume.

Example for setting up a SnapMirror relationship between two FlexClone volumes

You have two systems SystemA and SystemB. The SystemA system has a volume volA and the SystemB system has a volume volB. The volA and volB volumes are in the SnapMirror relationship where volA is the source volume and volB is the destination volume. A FlexClone volume cloneA is created from volA and a FlexClone volume cloneB is created from volB with a common base snapshot.

Establish the SnapMirror relationship between two FlexClone volumes by entering the following command on SystemB:

snapmirror resync -S SystemA:cloneA cloneB

If you are updating the /etc/snapmirror.conf file on SystemB, add the following entry to the file:

SystemA:cloneA SystemB:cloneB

-After updating the /etc/snapmirror.conf file, the following command establishes the SnapMirror relationship between the two FlexClone volumes:

snapmirror resync cloneB

Note: The SnapMirror relationship where cloneB is the SnapMirror source and cloneA is the SnapMirror destination is also supported. The cloneB FlexClone volume is created from the parent destination volume and the cloneA FlexClone volume is created from the parent source volume.