mdonovan
Contributor
Contributor

vmotion and performance loss on VMs

Lately some people here have been complaining about slowness in an application running in ESXi 5.5. The app runs fine for a while then slows down to a crawl for a while, then suddenly works ok again.

Vendor is pointing fingers and saying it's not them, so people here are suddenly latching onto vmotions as causing the slowness, even though the timing of all vmotions don't coincide with the slowness issue.

The vmotions are handled on their own switch, on their own nic port. Performance stats for the VMs in question show nothing unusual, host stats same.

Does anyone know about a document about vmotion that I can use to stop these attempts to blame vmotion just because they can't find anything else? Has anyone experienced slowness or vms going off the network due to vmotioning?

Thanks

Matt

Reply
0 Kudos
pratjain
VMware Employee
VMware Employee

If the vMotion is initated by DRS disable the vMotion for the Virtual machine for the time-being.

Steps to disable vMotion for a virtual machine in a DRS enabled cluster are

Right Click on your cluster and then click on "edit settings"

Under DRS, click on "Virtual Machine Options"

Locate the particular VM and the drop down box under "Automation Level"

Change "Default (Fully Automated)" to "Manual"

After changing the automation level to manual vMotion would not happen unless someone manually triggers it.

There have been issues virtual machine going off network due to vMotion but only assumptions can be made until we find the cause of the issue and this would be great place to start    

Regards, PJ If you find this or any other answer useful please mark the answer as correct or helpful.
Reply
0 Kudos
JPM300
Commander
Commander

Hey,


I agree with PJ, temporarly disable DRS for a day or so and if the slowness still occurs you can rule out vmotion and get that out of the equation then start looking at metrics in ESXTOP to see what the VM is doing when it has its "slowness"  Can this problem be replicated or is it just random?

Reply
0 Kudos
mdonovan
Contributor
Contributor

I have already disabled DRS on the VMs in question and they are still experiencing these problems. It's quite obvious to me that vmotion has absolutely nothing to do with it, but the application people are sticking with this fantasy because they have no other ideas. I was just wondering if anyone else had any problems with vmotion interfering with a VM's performance, so I can say that I checked and nobody has ever seen this issue.

The problem occurs randomly, and isn't reproducible that I'm aware of. The Linux guys look at the server and they see no issues with the OS either.

Matt

Reply
0 Kudos
JPM300
Commander
Commander

Hey,


putty into the host that runs the VM and check all the ESXTOP metrics:

http://www.yellow-bricks.com/esxtop/

It's possible you could have some storage latecy, CPU ready time, co-scheduling issues, or some other reason as to why this Vm has issue.  What does this VM acutally do? SQL, Fileserver, App server?

Reply
0 Kudos
mdonovan
Contributor
Contributor

I downloaded a GUI version of esxtop and used that. In the mean time the SAN has been experiencing issues, so I'm going to start pushing towards that angle and get them out of the "OH NO! A VMOTION!!" mindset.

Thanks for the responses though.

Matt

Reply
0 Kudos