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Delphix

Replicated Data Consumes More Space than the Original Source Data (KBA9019)

 

KBA

KBA# 9019

 

Issue

Replicated data may consume more space on the replication target engine than on the source engine if the target engine has experienced storage write errors in the past that have not been cleared.  This is caused by a difference in the way the blocks are written on the target engine in the presence of past write errors.  There are no implications for the correctness of the replicated data, only for the amount of space consumed within the storage pool.

Prerequisites

This can happen when the replication target Delphix engine has experienced write errors to its virtual disks in the past and these errors have not been cleared.

Applicable Delphix Versions

Click here to view the versions of the Delphix engine to which this article applies
Major Release All Sub Releases
6.0 6.0.0.0, 6.0.1.0, 6.0.1.1, 6.0.2.0, 6.0.2.1, 6.0.3.0, 6.0.3.1, 6.0.4.0, 6.0.4.1, 6.0.4.2, 6.0.5.0, 6.0.6.0, 6.0.6.1, 6.0.7.0, 6.0.8.0, 6.0.8.1, 6.0.9.0, 6.0.10.0, 6.0.10.1, 6.0.11.0, 6.0.12.0, 6.0.12.1, 6.0.13.0

5.3

5.3.0.0, 5.3.0.1, 5.3.0.2, 5.3.0.3, 5.3.1.0, 5.3.1.1, 5.3.1.2, 5.3.2.0, 5.3.3.0, 5.3.3.1, 5.3.4.0, 5.3.5.0, 5.3.6.0, 5.3.7.0, 5.3.7.1, 5.3.8.0, 5.3.8.1, 5.3.9.0

Resolution

If storage errors are present on the replication target engine, these should first be resolved.  Assistance may be required from Delphix Support to clear the errors on the engine.

Once any storage issues have been resolved, to correct the disparity in storage consumption, the data needs to be replicated again to ensure that the affected blocks are rewritten.  However, if this is not possible due to dependencies from child VDBs for instance, the disparity would be expected to be corrected gradually over time as changes to the source data are replicated to the target engine, rewriting the affected blocks on the target engine.

This issue will be addressed in a future Delphix release via bug DLPX-80122.

Troubleshooting

If a large discrepancy is found between the size of replicated datasets on the replication target engine and the sizes of the same datasets on the source engine, check for a 'Critical storage device error' on the Faults page of the engine's admin UI that was active at the time the replication was performed.

 

 


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