VM Settings vCPUS' and Memory shares

[marrag]

Hi,

i have a few questions about VM Resource settings and hope you could give me some best practice hints.

In which case is it usefull to give more than one vCPU to a VM? As i understand 2 vCPU's mean only the VM has twice as much cpu shares than a 1vCPU VM? I'snt that the same as setting the Resource Allocation to high ? Is there a true parallelisation when i give multi vCPUS to VM's?

What about RAM Eaters? We have four Develoment VM's with 2G of vRAM each (this is mostly a political decission to gain acceptance from our users). The most Time of the day RAM usage ist about 10 to 20%, only in high load Peak-times the usage is about 90 to 100%. No limitation and no reservation is done for the VM's. Is that a good practice, or is that resource wasting? Would'nt it be better to put those Maschines in a Resourcepool that has 2G of RAM guaranteed -> expandable. Should a Limit be set?

At this Time our HA DRS Cluster runs fine, no resource pools exist and no reservations or limitations are done at any VM. But we create new VM's daily. High Load productive Maschines and also Test or Developement Systems,and im interessted to get the best out of the underlying hardware.

greetings and thanks in advance for any hint

[jp-H]

Hi Narrag.

Concerning the VCPU, you analysis, is not exact. In fact each VCPU is able to use a different PCPU. It is not possible when a VM has only one VCPU. So in fact when a VM has 2 VCPU it can use at most 100% of each PCPU. When a VM has 1 VCPU the VM can be switched between 1 PCPU to another.

Concerning RAM, I "fight" with each user to give the correct level for the VM. Usualy I try to give all RAM needed.

Concerning DRS We created ressource pools to isolate test and dev. VM from Production VM.

Hope that helps you.

[marrag]

Hi, jp-H

thanks for your answer. So my Question about vCPU' s is answered. If i need to parallelize Tasks in Vm's i need multiple vCPU's.

How do you assure the RAM needed for a VM? Start low and watch the monitoring in VC?

[jp-H · Accepted solution]

Hi Marrag.

Yes exactly, usualy, i start slow and watch regularly. I also use a program witch collects regularly informations about the server health called "omnivision". it creates a database for each server and keep infos during long time on server health. If the server is needing memory or CPU I can see that inside. In fact you can do the same with virtual center. Just be carefull to confirm memory using by looking in the VM OS not only in VC.

[marrag]

Hi jp-H,

so i'm proved in may way of cluster management. I'll give that omnivion a try.

Thanks for your answers an have a nice WE.

[jp-H]

Thank you,

The week-end will be better than the week (because of big strikes in france since wednesday).

Have a nice week-end too.