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Is it possible to convert an XDP (SnapVault) relationship to a DP (SnapMirror) relationship in clustered Data ONTAP 8.2.1x?

Applies to

  • Product Model: FAS8040-R6
  • OS: Clustered Data ONTAP 8.2.1
  • Category 2: SnapVault

Answer

This is not a supported process.

DP mirrors use BRE (Block Replication Engine), which tracks each block and is unaware of file system structure. The engine that -type XDP mirrors, SnapVault and version independent SnapMirror, use is LRE/LRSE (Logical Replication Engine / Logical Replication engine with Storage Efficiency). LRSE tracks the data logically based on the file system structure. So when the resync is attempted, BRE cannot find any snapshots that hold block based references to the data so it reports that there are no common snapshots since the block based engine cannot understand the logical tracking.

If you attempt to convert a relationship, which was originally an XDP relationship to a DP relationship, and then attempt to resync back to the source it will fail with the following error message:

No common Snapshot copy found between <source> <destination>

If you attempt to convert a relationship, which was originally an XDP relationship to a DP relationship, and then attempt to update it, the snapmirror show command displays the following error message:

cluster_82b::> snapmirror update -destination-path vs2:vs2_sv_dest Operation is queued: snapmirror update of destination vs2:vs2_sv_dest
cluster_82b::> snapmirror show -destination-path vs2:vs2_sv_dest

Source Path: vs1_test:compress_test
Destination Path: vs2:vs2_sv_dest
Relationship Type: DP
SnapMirror Schedule: -
Tries Limit: -
Throttle (KB/sec): unlimited
Mirror State: Snapmirrored
Relationship Status: Idle
Transfer Snapshot: -
Snapshot Progress: -
Total Progress: -
Snapshot Checkpoint: -
Newest Snapshot: 5min.2015-05-04_0830
Newest Snapshot Timestamp: 05/04 08:32:57
Exported Snapshot: 5min.2015-05-04_0830 Exported Snapshot Timestamp: 05/04 08:32:57
Healthy: false
Unhealthy Reason: Transfer failed.
Constituent Relationship: false
Destination Volume Node: cluster-01
Relationship ID: 003d8e96-f25a-11e4-bbdf-123478563412
Transfer Type: -
Transfer Error: -
Current Throttle: -
Current Transfer Priority: -
Last Transfer Type: update
Last Transfer Error: Destination was previously used as the destination of an XDP relationship. Using an XDP destination volume as the destination volume for a DP relationship is not supported.
Last Transfer Size: -
Last Transfer Duration: -
Last Transfer From: vs1_test:compress_test Last Transfer End Timestamp: 05/04 08:41:14
Progress Last Updated: -
Relationship Capability: 8.2 and above
Lag Time: 0:8:20
SnapMirror Policy: DPDefault

According to Engineering, a DP relationship which is converted to an XDP relationship can be converted back to a DP relationship, IF the source and destination volumes still have Snapshots with the same instance and version UUIDs.

Additional Information

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