ESXi 5.1 U1, Powered on VM take snapshop takes more than 5 minutes

[langhunld]

Hi guys,

     I have several HP BL460c Gen8 server with ESXi 5.1 U1 installed, and the servers were managed by vCenter Server 5.1. The problem is when i taking snapshot on a powered on VM, it takes more than 5 minutes to complete the task.But if i take snapshot on a powered off VM, the task could complete within 2 second.

     I've tried to take snapshot via connect to vCenter server and connect to ESXi host directly, and the result is the same: taking snapshot on a powered on VM always takes several minutes to complete, while taking snapshot on a powered off VM only takes 1 or 2 second. Also I've tried to enable and disable write-cache on BL460c Gen8 server, nothing changed. Tried to install ESXi 5.1 WITHOUT update1, still not helping. Of course, all the ESXi image is HP oem ESXi image. I refered to the KB http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&docType=kc&externalId=1021386&sl..., it did reduced the time but still takes more than 30 seconds. All the VM i tested were totally free, no app is running and no app is installing, all the VMs installed the corresponding VMware tools, all the VM tested were installed with WinSvr 2008 R2 SP1.

     Any suggestion?

[DavoudTeimouri]

Hi,

How many you have disk space on the virtual machines?

Based my experiences, this is depended to virtual machine running tasks, CPU usage and host memory usage by VM also VM size.

As you know, many services are running on a Windows server and they are writing on the disk. So taking snapshot on 5 minutes and more is normal.

Check create snapshot from a VM with client OS and compare the results.

[ElevenB2003]

Are you specifying where to store the VM's swap files? Are you specifying to snapshot the virtual machine's memory?

[memaad]

Hi,

Snapshot creation takes time depending upon memory allotted to virtual machine, since it has to flush data from memory to base disk and then create delta disk.

Regards

MOhammed

[langhunld]

thanks for all the reply.

I performed some further test on the VM, if i uncheck "snapshot the virtual machine's memory" option, the task could complete very soon, and if doing the snapshot with "snapshot the virtual machine's memory" option check by default the task would take a long time. According to my test, take a snapshot on a powered on VM with 2GB memory takes about 90 seconds, a powered on VM with 4GB memory takes about 4 minutes, a powered on VM with 8GB memory or higher may need more than 7 minutes.

All the VM's swap files were stored in the same position with the VM files in a FC SAN LUN, and the VM is totally idle while taking snapshot.

Does anyone of you has similar test result? Does my vSphere environment going normally?

[Omega42]

The Snap seems to be able to write about 20MByte/s to disk.

It seems a bit slow to me, but my test only shows a little bit more.

This could be slow storage or simply the fact that esx tries to keep the vm running while snapshotting and memory changes even in an "idle" vm very heavily.