IBM Support

Low dedup ratio on virtual copy storage pool stored on a target server

Question & Answer


Question

The " Duplicate Data Not Stored:" reported by the "QUERY STG Dedup_source_pool" command on a source server is much higher than the ratio reported by " QUERY STG Dedup_target_pool" command on a target server for the virtual copy storage pool.

Cause

Working as designed

Answer

During normal backup to a deduplicated primary storage pool, if the files are same, the data will be dedupped. So a high dedup ratio would be expected the same files are backed up.
During backup storage pool to a remote deduplicated virtual storage pool, a virtual volume is actually stored as an archive file on the target server. The archive file on the target server contains the client files as well as metadata for virtual volumes. This metadata can be different although the client files are the same. As a result, the dedup ratio on a remote virtual storage pool will be lower than the source primary storage pool even though they store the same client files.

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Document Information

Modified date:
17 June 2018

UID

swg21567152