Resync SnapMirror workflow

Goal

The Resync SnapMirror workflow starts a resynchronization operation to either reestablish a SnapMirror relationship that is broken or to reestablish a SnapMirror or SnapVault relationship whose updates have failed due to deletion of a common Snapshot copy from the source volume.

Prerequisites

You must be running Clustered Data ONTAP 8.2 or later.

About this workflow

This workflow is typically invoked in the following circumstances:

·         A SnapMirror relationship is broken (that is, the destination volume is a read/write volume and no longer a data protection mirror).

For example, a storage administrator sees a broken SnapMirror relationship and he wants to reestablish the relationship.

For example, a storage administrator notes that SnapMirror or SnapVault transfers are failing because a required common Snapshot copy is missing from the source volume.

·         To create a SnapMirror or SnapVault relationships between two volumes that are not in a data protection relationship but have a common Snapshot copy.

For example, a storage administrator identifies two volumes that have a common Snapshot copy but are not in a SnapMirror or SnapVault relationship and he wants to establish a new relationship between the two volumes.

Additional considerations concerning this workflow include the following:

·         The resync operation will fail if the destination volume does not have a Snapshot copy in common with the source volume.  

·         The resync operation might cause data loss on the destination volume because this operation might remove the exported Snapshot copy on the destination volume.

WFA user actions

1.       Click Portal > Data Protection > Resync SnapMirror to display the Executive Workflow dialog box for the Resync SnapMirror workflow.

2.       Specify values for the appropriate inputs.

·         If you are resynchronizing  a broken SnapMirror relationship between the original source volume and original destination volume, or because a required Snapshot copy was deleted on the source volume and SnapMirror transfers are failing, the following user inputs apply:

·         Destination Cluster (mandatory)

·         Destination Storage Virtual Machine (mandatory)

·         Destination Volume (mandatory)

·         Maximum Transfer Rate

·         Transfer Priority

·         Source Snapshot

·         If you are resynchronizing because a required Snapshot copy was deleted on the source volume and SnapVault transfers are failing, the following user inputs apply:

·         Destination Cluster (mandatory)

·         Destination Storage Virtual Machine (mandatory)

·         Destination Volume (mandatory)

·         Maximum Transfer Rate

·         Transfer Priority

·         Preserve

·         If you are resynchronizing to establish SnapMirror relationship between two volumes that are not in a data protection relationship but do have a common Snapshot copy, the following user inputs apply:

·         Destination Cluster (mandatory)

·         Destination Storage Virtual Machine (mandatory)

·         Destination Volume (mandatory)

·         Source Cluster (mandatory)

·         Source Storage Virtual Machine (mandatory)

·         Source Volume (mandatory)

·         Maximum Transfer Rate

·         Transfer Priority

·         Source Snapshot

 

 

3.       Click Execute.

 

User input descriptions

User Input

Description

Destination Cluster

(Mandatory)

Cluster where the destination volume resides

Destination Storage Virtual Machine  (Mandatory)

Storage Virtual Machine (SVM) where the destination volume resides

Destination Volume (Mandatory)

The destination volume for this resync operation

Source Cluster

(Optional)

Cluster where the source volume resides.  

A value must be specified if the destination volume is not in a SnapMirror or SnapVault relationship.

Source Storage Virtual Machine (Optional)

Name of the SVM where the source volume resides.

A value must be specified if the destination volume is not in a SnapMirror or SnapVault relationship.

Source Volume

(Optional)

Name of the source volume for the resync operation.

A value must be specified if the destination volume is not in a SnapMirror or SnapVault relationship.

Maximum Transfer Rate

(Optional)

Maximum transfer rate, in kilobytes per second, at which data is transferred.

The default (0) is unlimited which permits the SnapMirror relationship to fully utilize the available network bandwidth.

Transfer Priority

(Optional)

Priority at which the resync operation runs.

The default value is the value specified in the SnapMirror policy associated with the relationship.

Valid values are: low, normal

Source Snapshot

(Optional)

Snapshot copy on the source to use for the resynchronization operation. This input affects the transfer operation in different ways depending on whether the relationship is SnapMirror or SnapVault and whether the source volume type is read/write or data protection. See “Snapshot copy transfer behavior” below for details.

Preserve

(Optional)

This parameter only applies to SnapVault relationships.

If the value is False, all Snapshot copies on the destination that are newer than the latest common Snapshot copy are deleted by the resynchronization operation.

If the value is True, newer Snapshot copies are retained.

The default value is False.

Snapshot copy transfer behavior

Depending on the relationship type or source volume type, your input or omission of input to the Source Snapshot field affects the transfer operation behavior in the following manner:

 

SnapVault relationship Snapshot copy transfer behavior

SnapVault behavior when source is read/write

SnapVault behavior when source is Data Protection (DP)

Transfers the selected Snapshot copy.

Source Snapshot copy selection is not supported for data protection volumes.

 

SnapMirror relationship Snapshot copy transfer behavior

SnapMirror behavior

SnapMirror behavior when relationship is second hop in a SnapMirror to SnapMirror cascade

Transfers all Snapshot copies from the source, up to and including the selected Snapshot copy.

Source Snapshot copy selection is not supported for data protection volumes.

 

Workflow description

When completing the default Resync SnapMirror workflow, WFA executes the following tasks:

1.       Search for source volume. WFA calls the No-Op Cluster-Mode command to search for the source volume of the resync operation.

2.       Resync SnapMirror. WFA calls the Resync SnapMirror command to start the operation to re-establish a SnapMirror or SnapVault relationship between a source volume and a destination volume.

The resync operation runs in the background on the source and the destination clusters. The Resync SnapMirror command does not wait for the operation to finish.

Results

After the resynchronization operation completes, the SnapMirror or SnapVault relationship can be manually updated or scheduled for updates.

Customization

You can customize the default Resync SnapMirror workflow to clean up the original broken SnapMirror relationship.

 

Depending on the amount of data to be resynchronized, the resynchronization operation between the source volume and the destination volume might require several hours or days to complete; therefore, the default Resync SnapMirror workflow does not wait for the resynchronization process to finish. 

 

If you want to customize the Resync SnapMirror workflow to monitor the operation and wait for it to finish, you can complete the following step:

 

1.       Add a task to the workflow that contains a Wait for SnapMirror Resync command to monitor the resync operation and wait for it to finish. No specific WFA command is supplied for this purpose, but you can create one by using the WFA command editing function to clone the current Wait for SnapMirror Initialization command and then customize the clone to monitor the progress of a SnapMirror resync operation.  The workflow succeeds only if the resynchronization operation finishes successfully.