ESXi snaps with memory taking longer to create on Nimble than other storage

[ron_fisher]

Greetings,

Mind you I do not promote the use of vmware snaps for anything but the most short term use possible. That said, I've been doing some basic functionality testing of my vSphere 5.5 cluster, 9 BL460's software iSCSI connected over meshed 10GE to a new CS-500 (just upgraded to 2.2.5). So far things are blazing fast, MPIO is well balanced and I'm getting terrific compression using eager zeroed thick vmdk's.

I just noticed on two different VM's that if I do a vmware snap and include memory, the snap takes a crazy long time to create versus a VM on my fiber channel connected VNX. Leave off the memory and it it fast as it should be. I monitored file creation using the vmware datastore browser and all the diff files and snapshot memory files are created very quickly but the snap takes 15+ minutes for smaller vm's and close to an hour for a large (64GRAM with 3T storage (compressed to 600G thank you very much!).

I view the process in the Nimble console I see a constant stream of writes (300 IOP's) during the whole process.

Something to do with Compression on the Nimble or something else?

Thanks for any insight

R

[#2]

Ron,

  When you took the VMware-based snapshot of the VM on your 'Echo Mary Charlie' array, was it the *exact* same VM that's running on the Nimble?  If you have a lot more memory access going on with the Nimble-stored VM (say, it's a file server servicing many inbound clients, reading and writing) and, say, a different VM (that's idle) on your 'Charlie array, I'd expect that the VMware-based snapshot process would run *way* slowerm, as it has to quiesce the VM and write out the memory contents.  If you didn't storage vMotion the same VM between the two arrays, I'm afraid it's not quite a fair comparison!     Note: I'm basing some of my commentary from a similar thread found on VMware's community site: Why are snapshots with memory so slow? | VMware Communities

  So....apples to apples, or apples to oranges?

   Thanks for your patience, Ron!

-Neil

[ron_fisher]

I think it was a fair comparison that I tried on vm's of various sizes none of them loaded with user sessions. Note quiesing is an optional component of a snapshot and one that I did not include. The VNX is at capacity and running most of our environment while the Nimble has next to nothing on it. So just to be sure I just did a snap of a small 2GRAM/40Gig of storage vm on the VNX. 45 seconds with memory. delete snap and svmo to the Nimble... the time was quicker.. 25 seconds. Hmmm. So try a larger 8GRAM/600 gig of storage. 6 minutes to snap with mem on the VNx. Move it to the Nimble... and 6 minutes to snap.

The difference between two days is I've move little more load onto the Nimble.  Must have been cache warm up

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