Dedup and Zero Detect

[apol]

Hi,

is it ok and does it make any sense to enable both dedup and zero detect on the same volume? I thought that dedup is more or less a superset of zero detect and left zero detect off for dedup volumes, but apparently automatically created secondary volumes have both features enabled (both 3.2.2 and 3.3.1 do this).

[Sheldon Smith]

Agreed. As noted in the HPE 3PAR Storage—Adaptive Data Reduction Technologies technical paper (a00006358ENW, December 2017, Rev. 2):

"With HPE 3PAR Deduplication, there are internal differences in the way space reclaim operates. With dedup VVs, it is not necessary to have a zero-detection mechanism to scan all incoming I/Os as all zero blocks will be reduced to a single zero block by the deduplication engine."

"...it is not necessary..." So I don't think it's a problem, but please check with Support if you haven't already.

"...automatically created secondary volumes..."

What is creating these volumes? Are you talking about Remote Copy secondary volumes?
If so, how are you having them created? Command line, SSMC, other? And if not the command line, what version of tool?

[apol]

Yes, Remote Copy secondary volumes. Created with either SSMC or up-to-date cli "admitrcopyvv -createvv ...". The primary vv has only dedup, the secondary ends up with dedup AND zero detect.

I'm just wondering if streamlining vv-settings over 25+ 3PAR-Systems is worth the effort, or if this difference does not have any impact (ASIC workload, service time, remote copy...).