VM Performance on DRS with non shared storage

[CapiZikus]

We have 4 identical servers at the same location with vcenter, each server has it own storage-DAS attached to it (not an ideal & tried VSA which we dont like also).

We are also planning to put all VM from those DSA to SAN in future so that we can do all the load balance feature, ie vMotion, migrate etc.

We have created a new cluster and put all servers into a same farm, turn on the DRS so that we could prepare DRS group in advance.

We then created a new resource pools, with default setting such as unlimited CPU and memory, share set to normal; then we move some VMs in to those pool. As above each server not have a share storage yet so these VM will not try to power on on a other host nor suggest/automate to different host..

My question is, are those VM will be decreased any performance at all?

[weinstein5]

As long as there are sufficient resources on each host there should not be any decrease in performance - I would disable DRS since it is not doing anything and will put an additional load on your vCenetr server

[CapiZikus]

@ Weinstein5 - Thanks for the quick respond.

In DRS, for example the each server has 50GHz, and 128G RAM each (4 servers), therefore CPU limited is 200G, 512G RAM,

I have created a DRS set to HIGH then reservation set to 40GHz and memory reservation is 100G RAM for our production; is this means DRS will spitted the reservation of 40GHz and 100G RAM across the cluster member? or to just one server?

The production VM that we have think it might degraded performance is only consumed, 30GHZ and 16GRAM on a specific server, there is plenty of resources, no over provision both CPU and memory on the server either or it is just a co-accident?

Been trying to read up some article but could not find one.

[sajal1 · Accepted solution]

Hi CapiZikus,.

DRS creates a resource pool and the resources are distributed to all the Hosts. The reservation is not limited to a particular host. But remember a single VM resources can not come from multiple resources. For example:

Say you have 3 hosts with 10 Ghz and 20 GB RAM each. So if you create a DRS cluster and resource pool you have a resource pool of 30 Ghz CPU and 60 GB RAM.

But if you create a VM of say 15 Ghz CPU and 30GB RAM then it is going to be over provisioned for a host. The normal resources of the VM will be limited by the physical resource limitation of the Physical host only (which in this case is 10 Ghz and 20 GB RAM). If you provision more than that in a VM it will be over provisioned for that VM.

Hope this clears a bit.

For more information consult the following document:

http://pubs.vmware.com/vsphere-55/topic/com.vmware.ICbase/PDF/vsphere-esxi-vcenter-server-55-resourc...