VSA replication - Different Size on disk between source and target

Dear All,

We are testing two Storeonce VSA systems with one vtl replicated on the other VSA vtl.
Could you explain us why we have differences in Size on disk between Source and Target?

For example we have a source size on disk (dedup) of 338GB and a target size on disk (debup) of 778GB.

Thanks in advanced,


  • Verified Answer

    Hi Salvatore,

    Based on my experience it is related how the StoreOnce target receives data by replication from source.

    Imagine the backup server writes a data stream to the VTL. StoreOnce performs an inline deduplication of the data stream by performing chunking, hashing and matching to find corresponding parts already stored on disk. During this process data is reduced as good as possible before written to disk.

    When data is replicated the source StoreOnce reads the data from disk and sends it across in a preprocessed form. Usually the data streams are assembled differently resulting in different deduplication results on source and target. I've seen cases where the destination system had better deduplication results than the source.

    Is there anything special related to the backup data? Is the data pre-compressed, encrypted, contains a lot of images or videos? This could explain what you see.

    If the backup application is Data Protector then you should consider StoreOnce Catalyst over any VTL emulation. This allows you to control replication from the backup application.

    Please use the Accept Solution button next to my post and assign a KUDO (thumbs up icon) if this works for you.

    Sebastian Koehler