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understanding dedup in 3.3.1
https://3parug.net/viewtopic.php?f=18&t=2984
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Author:  oneill [ Wed Sep 12, 2018 1:28 am ]
Post subject:  understanding dedup in 3.3.1

I have just update to 3.3.1 MU2.
After that in the 3par management console version 4.7.3 under virtual volumes I have a new volume named .sysvv_0SSD_r5 that was not ther before.
If I use SSMC I do not see that volume.
Then I have the virtual volume published to xenserver hosts.
Here what I see:
Total used: 24,14 GiB
Virtual size: 7.144,00 GiB
Total reserved 24,50 GiB
Host written 1.639,11 GiB

and it says used 0%

If I make the sum of my VM I have about 2TB, considering that disk are not full I am guessing that the value in Host written is correct with the space used by VM.

So how is possible that total reserved is 24GB only?

In that hidden virtual volume ( .sysvv_0SSD_r5) I have 1.2 TB


Someone can explain to me how 3.3.1 use space? thanks

Author:  JohnMH [ Wed Sep 12, 2018 8:40 am ]
Post subject:  Re: understanding dedup in 3.3.1

.sysvv_0SSD_r5 is the common dedupe store for the CPG, with 3.3.1 matching pages will be stored in this volume, unique pages will be stored in the regular VV you present to the host, unless there is a match in which case it will be migrated to the dedupe store. So the two combined will be the sum of the data stored on the backend.

See this whitepaper for more detail https://h20195.www2.hpe.com/v2/getdocument.aspx?docname=a00006358enw

"The dedup ratio of a CPG is the sum of all the data written (host written) to the deduplicated volumes divided by the sum of the data stored in the volumes and the data associated with the volumes in the Dedup Store."

Author:  MammaGutt [ Wed Sep 12, 2018 3:01 pm ]
Post subject:  Re: understanding dedup in 3.3.1

.sysvv is tdvv1/2. Tdvv3 should be .shared if my memory serves me right. Showcpg -d should show dds version I think.

Author:  oneill [ Thu Sep 13, 2018 9:52 am ]
Post subject:  Re: understanding dedup in 3.3.1

MammaGutt wrote:
.sysvv is tdvv1/2. Tdvv3 should be .shared if my memory serves me right. Showcpg -d should show dds version I think.


Here the output:
cli% showcpg -d
----Volumes---- -Usage- ----------(MiB)----------- --LD--- -RC_Usage- -Shared-
Id Name Warn% VVs TPVVs TDVVs Usr Snp Base Snp Free Total Usr Snp Usr Snp Version
0 FC_r1 - 0 0 0 0 0 0 0 0 0 0 0 0 0 -
1 FC_r5 - 1 0 0 1 0 6967296 0 0 6967296 13 0 0 0 -
5 FC_r6 - 0 0 0 0 0 0 0 0 0 0 0 0 0 -
2 SSD_r1 - 0 0 0 0 0 0 0 0 0 0 0 0 0 -
3 SSD_r5 - 2 0 1 2 0 1522688 0 602112 2434816 0 10 0 0 2
4 SSD_r6 - 0 0 0 0 0 0 0 0 0 0 0 0 0 -
----------------------------------------------------------------------------------------------
6 total 3 0 8489984 0 602112 9402112 13 10 0 0

what is tdvv3? I have just upgrade to 3.3.1 but the cpgs and virtual volumes where created before with 3.2.2
I have done a tune on the virtual volume. Is there anything else I have to do to use the increased depup performance of 3.3.1?

Author:  MammaGutt [ Thu Sep 13, 2018 3:08 pm ]
Post subject:  Re: understanding dedup in 3.3.1

You need to create a new CPG and tune all volumes to that CPG or convert all tdvvs to tpvv and once all are gone you convert them back.

Author:  anders.dicker [ Mon Nov 29, 2021 6:20 am ]
Post subject:  Re: understanding dedup in 3.3.1

Is there someone having experience on any performance impact for the final release of dedup version 2 space?

I was finally able to migrate all data on one side of a peer-persistence configuration to new dedup version 3. And now everything is running fine on new dedup version 3 LUNs. But the old CPG still has roundabout 50 TB of disk space for version 2 deduplication in use.

Is it safe to remove the last dedup volume from this CPG during normal working hours? Is a compact_cpg necessary afterwards to free up the space or do I get this disk space back instantly? Or would it be better to temporarily switch back to the other side (with all LUNs still being dedup v2), stop all rcopy groups and delete the last LUN on an idle system? :?:

Author:  cali [ Wed Dec 29, 2021 9:10 am ]
Post subject:  Re: understanding dedup in 3.3.1

If you delete the Old empty CPG, the Dedup 2 Store should be also deleted.
Read also here: viewtopic.php?f=18&t=2645

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