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SSD CPG with one replicated Volume https://3parug.net/viewtopic.php?f=18&t=3395	Page 1 of 1

Author:

storage-guy90 [ Tue May 05, 2020 8:18 am ]

Post subject:

SSD CPG with one replicated Volume

Hey guys,
I have an question to my 3PAR 7400.

We got two indentical systems (3PAR1 & 3PAR2), and each system have an SSD-CPG. Every system includes on volume.
The 3PAR replicate the volume from 3PAR1 to 3PAR2 via Thin-Persistence synchronous.

We got an message, that the "Total SSD raw space 85% usage threshold" is allocated, but only on the 3PAR1 and not the 3PAR2. I check both 3PARs via CLI and don't understand, why the volumes have different values for dedup and capacity? The values are in sync!

Any ideas?

Attachments:

File comment: 3PAR2 - Target
Command:
showspace and showvv

3par2.JPG [ 39.24 KiB | Viewed 12511 times ]

File comment: 3PAR1 - Source
Command:
showspace and showvv

3par1.JPG [ 39.6 KiB | Viewed 12511 times ]

Author:	MammaGutt [ Tue May 05, 2020 11:20 am ]
Post subject:	Re: SSD CPG with one replicated Volume
Dedupe.... I'm guessing you're doing tdvv1 (cpg created on 3.2.2 or earlier). With tdvv1, all values in showvv is weighted numbers based on DDS size, number of volumes and how much is written to those volumes. As far as I can see, you only have one volume in the CPG so the volume stats are the stats for the entire DDS. Either way with this dedupe ratio, you shouldn't do dedupe. Anything below 1.4:1 just isn't worth it.

Author:	storage-guy90 [ Wed May 06, 2020 1:50 am ]
Post subject:	Re: SSD CPG with one replicated Volume
Thanks for your response. Yes correct is a tdvv1. But what I'm not understood. This is a synchronous volume (peer persistence) what replicate the written data immediatly from 3PAR1 to 3PAR2. Why are the sizes from ADM/SNAP/Reserved from this both volumes different? For my understanding: When I have a Peer-Persistence Volume that save the same data on both volumes, why differe the value of space and dedupe?! I can't get this into my head!

Author:	MammaGutt [ Wed May 06, 2020 5:58 am ]
Post subject:	Re: SSD CPG with one replicated Volume
The volumes might be exactly the same, but the DDS for the CPG isn't on these two systems. The 3PAR can't tell you exactly how big a dedupe volume is and neither can you. Because there is no good way of presenting the blocks that dedupe.

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