Suspend a whole set of VMs to improve performance during performance tests?

[yeayu]

Hello all,

I was wondering whether someone can give an answer or at least point out what are the benefits and constrains regarding the following assumption:

Would it help to suspend a bunch of VMs (over 100 VMs) to improve performance on several other VMs running application performance tests?

Basically, a department within my company relies on VMware vSphere 5.x environment to run different performance tests.

During a normal day, several heavy resource dependand tests are run on different groups of VMs. Once a test has finished (it usually takes around 3 - 4h), the machines belonging to that group are not used anymore until next day.

I would like to improve the current resource utilization and (if possible) speed up the time involved on those tests; would it help then to suspend all the machines not needed until next day to free up as much host resources as possible?

Assumming that the idea is feasible, does anyone have an idea of what might be the contrains of trying to resume 100 VMs at once?

On the other hand, if this is totally crazy; what other approaches might work?

Thanks in advance

[DavoudTeimouri]

Hi,

You can do it via PowerCLI. please read this article: VMware KB: Suspending a virtual machine on ESX/ESXi to collect diagnostic information

[yeayu]

I know that can be done through powercli.

What I am interested in knowing is if that will really behave as I am predicting; what are the downsides? any concerns to keep in mind?

[DavoudTeimouri]

I think, just your storage capacity and I/O will be impacted during this process because current state of the VMs memory will be saved on datastore.

I don't know about anything that may be happened when you are suspending many virtual machines on your environment.

[vfk]

Boot storm, this is typically VDI issue, but I think it applied here if you resume all of them at once and this will but load on your storage.

[JPM300]

If the VM's are not used till the next day and just idle on your ESXi 5.x hosts they won't be putting that much IO on your SAN or Mem/CPU on your hosts.  The only real advantage of pausing them or shutting them down I could see is if you want to re-claim that memory / CPU they are using.  However if your hosts are not under contention, then I would say just let them buck as it would prevent a boot storm like vfk mentioned.

[MagnetBoy]

Hello,

it all depends on resources(CPU, RAM, disk-I/O, etc.)

Two scenarios:

1. Host's resource utilization is higher than 50%
   1. then power off the unneeded VMs AND...
   2. assign more resources(CPU, RAM, etc.) to the test VMs.
2. Host's resource utilization is below (i would say) 30%
   1. then, there is no need to power off the VMs, AND...
   2. assign more resources to the test VMs, but
   3. make sure host resource utilization stays around 75%

It doesn't help if you just power off the unneeded VM's without assigning more resources to the test-VMs!

have fun!