topic Re: ESXi snaps with memory taking longer to create on Nimble than other storage in Array Performance and Data Protection

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

ron_fisher — Fri, 20 Feb 2015 23:32:37 GMT

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

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

Tue, 24 Feb 2015 20:49:35 GMT

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

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

ron_fisher — Tue, 24 Feb 2015 22:57:41 GMT

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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