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TDVV3 and shared space
https://3parug.net/viewtopic.php?f=18&t=2986
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Author:  gingerprince [ Fri Sep 14, 2018 7:09 am ]
Post subject:  TDVV3 and shared space

I've been doing some comparisons on an 8450. Initially created some deduped volumes - total CPG space consumed around 11TB, of which the .shared volume was 4.1TB. I then tuned them to a new CPG as DECO volumes - the total capacity used reduced to 7.7TB, but the .shared area was still 4.1TB. This is a new shared area in a new CPG, so it's not that it didn't shrink.

This seems to imply that even with compressed volumes, the common blocks in the .shared area are not compressed. Does anyone know for sure if that is the case?

Thanks

Author:  MammaGutt [ Fri Sep 14, 2018 9:19 am ]
Post subject:  Re: TDVV3 and shared space

With DECO it will first try to dedupe, if it hits on dedupe it will stop there. If it misses it will try to compress and pack it.

If you compress a block and pack it, it will never dedupe. So it is as designed that the DDS/.shared area will be identical in size for dedupe and DECO volumes.

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