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Managing a SnapVault-mirror cascade when the SnapVault backup is unavailable

You can manipulate relationships in a SnapVault-mirror cascade to maintain data backup relationships if the secondary of the SnapVault relationship becomes unavailable.

Before you begin

You must have a SnapVault-mirror cascade already configured.

About this task

The destination of the SnapVault relationship is the middle of the SnapVault-mirror cascade. If it becomes unavailable, you might have the following issues:

To manage this issue, you can temporarily remove the SnapVault secondary volume from the cascade and establish a SnapVault relationship to the mirror copy of the SnapVault secondary volume. When the unavailable secondary volume becomes available, you can reestablish the original cascade configuration.

In the following steps, the primary volume of the cascade is called "A", the secondary volume of the SnapVault relationship is called "B", and the destination volume of the data protection mirror relationship is called "C".

Steps

  1. Identify the current exported Snapshot copy on C by using the volume snapshot show command with the -fields busy parameter.
    The busy field is set to true for the exported Snapshot copy.
    Example
    volume snapshot show C -fields busy
  2. Break the data protection mirror relationship by using the snapmirror break command on C.
    Example
    snapmirror break C
  3. Create a dummy snapmirror-label on the exported Snapshot copy you previously identified by using the volume snapshot modify command with the -snapmirror-label parameter.
    If a snapmirror-label already exists for the exported Snapshot copy, you do not need to perform this step.
    Example
    volume snapshot modify -volume C -snapshot name -snapmirror-label exp1
  4. Create a Snapshot owner on the exported Snapshot copy of C by using the snapmirror snapshot-owner create command.
    This prevents clustered Data ONTAP from deleting the Snapshot copy.
    Example
    snapmirror snapshot-owner create -volume C -snapshot exported -owner admin1
  5. Delete the data protection mirror relationship between B and C by using the snapmirror delete command.
    Example
    snapmirror delete C
  6. Create the SnapVault relationship between A and C by using the snapmirror resync command and the -type XDP parameter.
    Example
    snapmirror resync -source-path A -destination-path C -type XDP
    You can maintain this SnapVault relationship until you recover the original SnapVault secondary volume. At that time, you can reestablish the original cascade relationship by using the steps that follow this step.
  7. Delete the data protection mirror relationship between A and B by using the snapmirror delete command.
  8. Perform a disaster recovery resynchronization from C to B by using the snapmirror resync command.
    Example
    snapmirror resync –source-path C –destination-path B
    This step copies from C to B, all of the Snapshot copies made after B became unavailable.
  9. Identify the current exported Snapshot copy on B by using the volume snapshot show command with the -fields busy parameter.
    Example
    volume snapshot show B -fields busy
    The busy field is set to true for the exported Snapshot copy.
  10. Break the data protection mirror relationship by using the snapmirror break command on B.
    Example
    snapmirror break B
  11. Create a dummy snapmirror-label on the exported Snapshot copy you previously identified by using the volume snapshot modify command with the -snapmirror-label parameter.
    Example
    volume snapshot modify -volume B -snapshot name -snapmirror-label exp2
    If a snapmirror-label already exists for the exported Snapshot copy, you do not need to perform this step.
  12. Create a Snapshot owner on the exported Snapshot copy of B by using the snapmirror snapshot-owner create command.
    This prevents clustered Data ONTAP from deleting the Snapshot copy.
    Example
    snapmirror snapshot-owner create -volume B -snapshot exported -owner admin1
  13. Delete the data protection mirror relationship between C and B by using the snapmirror delete command.
  14. Perform a SnapVault resynchronization from A to B by using the snapmirror resync command and the -type XDP parameter.
    Example
    snapmirror resync –source-path A –destination-path B –type XDP
    New Snapshot copies that meet the Snapshot policy of the SnapVault relationship are transferred from A to B.
  15. Delete the data protection mirror relationship between A and C by using the snapmirror delete command.
  16. Perform a disaster recovery resynchronization from B to C by using the snapmirror resync command.
    This step copies from B to C, all of the Snapshot copies made after reestablishing the A to B relationship without deleting any Snapshot copies on C.
    Example
    snapmirror resync –source-path B –destination-path C
  17. Remove the Snapshot copy owner from volumes B and C by using the snapmirror snapshot-owner delete command.
    Example
    snapmirror snapshot-owner delete -volume B -snapshot exported_snap
  18. Remove SnapMirror labels that you created from volumes B and C by using the snapshot modify command.
    Example
    snapshot modify -volume B -snapshot exported_snap -snapmirror-label text
    Example
    snapshot modify -volume C -snapshot exported_snap -snapmirror-label text