VMware Cloud Community
ntshane
Contributor
Contributor

Guest OS slow after vmotion

I've seen several threads about this problem with older versions of ESX, but not on ESX 4.  I am not running DRS at the moment.

ESX version:  4.0.0 build 261974

Vsphere vCenter version: 4.0.0 Build 258672

Problem: After vmotion, guest vm's become very sluggish for some time.  Sometimes the process taking up the cpu is the 'system' (not system idle) process.  However, this is not always the case.  Earlier today, I performed a vmotion on an Exchange CAS server and the system process was not the one taking up cpu cycles (instead it was the other processes such as IIS worker processes/etc).

Not sure where to go with this, I read about this problem occurring in older versions of esx and vcenter server when DRS was enabled.  I disabled DRS but still have the problem.  The cpu spike lasts anywhere from a few minutes to nearly an hour.

Reply
0 Kudos
7 Replies
ZMR
Contributor
Contributor

Check for CPU Cycling, in instance if this particular VM has more resources allocated then other VM on that server resulting in the slowness cause probably cpu cycling on the esx host with low resources.  You might want to look into that. Try going through ESXTOP on the ESX host to know for sure if that is the cause.

Reply
0 Kudos
ntshane
Contributor
Contributor

OK, so this is getting stranger.  The guest in question does not show up in the list of processes when I run esxtop.  I checked all three hosts in the cluster and it is not there.

-shane

Reply
0 Kudos
ZMR
Contributor
Contributor

If you like, just check on the VM summary in VI client it will show you which ESX that VM is currently registered to in cluster. vmware-cmd on that host and look for your VM to confirm it is registered on that host. Then troubleshoot through ESXTOP. From GUI I would look up that host itself and confirm enough resources regarding CPU, memory and performance chart . Second I would compare other VMs on that host with this particular VM for resource allocated to this VM. I believe most likely it is that this VM has more CPU and Memory assign then rest of the VMs on that host. I do not know the environment but if I had to guess I would say may be 4 - 8 CPU assigned for this one VM memory from 4 - 16 GB. While other VMs are half that. This is if you do not want to go through esxtop this would be one way to take an educated guess through VC

Reply
0 Kudos
ntshane
Contributor
Contributor

Oops! Sorry, I'm a dummy.  Hadn't expanded my console window far enough.  Still, the server seems to have settled now, but I know if I do another vmotion, it will slow down again.

Reply
0 Kudos
ntshane
Contributor
Contributor

I'm also finding that swpwt% on esxtop goes very high immediately after vmotion.

Reply
0 Kudos
ZMR
Contributor
Contributor

SWPWT are swapped pages to be read from disk, cause of slowness could possibly be memory overcommitment on that VM.

Look up SWPWT in the document to point you towards a better understanding and further troubleshooting

http://communities.vmware.com/docs/DOC-9279

ntshane
Contributor
Contributor

Thanks, but what is strange is that even when not overcommited with respect to memory, I get slowness after a vmotion.  Wasn't always this way.

Reply
0 Kudos