Is DRS & HA cluster vm shares aware ?

[Junior_FR13]

Hello,

We actually make a cluster design and decide to implement share on VM.

The cluster will be DRS and HA enabled and be composed of 3 ESX (VC 2.5up3 and ESX 3.5up3).

However, if the cluster HA current failover capacity is 0 (the 3 members use 80-90% of RAM ressource for example) and the ESX that execute big shares VM (on RAM) crashes, what happen ?

I deactivate the HA admission control on the Cluster, but if the biggest share VM has RAM reservation, the 2 other ESX will force lowest share VM to swap to free up phyisical RAM for biggest share VM reservation ? Or the biggest share VM won't start because ESX cannot offer RAM reservation ?

Thanks in advance.

[NTurnbull]

Hi, take a look at the Resource Management Guide Page 56 outlines resource pools and clusters with HA and DRS and then goes through clusters in the next 3 chapters.

Thanks,

Neil

[Junior_FR13]

Thanks,

I had re-read this document but i didn't find my information.

I re-read my post too, and maybe i wasn't clear :smileygrin: .

So i'm trying to explain again (differently) :

- I have 3 host in a cluster. For example ESX01, ESX02 & ESX03

- I have a lot of VM on this cluster, but on the VM01, I put 50000 RAM share, and on the VM02, I put 1500 RAM share.

- VM01 has 1024MB RAM reservation. No reservation on VM02.

- The VM01 is running on ESX01, and the VM02 on the ESX02.

- ESX01 crash, and there isn't enough ressources on the two other ESX to permit correct admission control of VM01.

The question is : As the VM01 share is biggest than the VM02 share, is the cluster forcing VM02 to use is vm swap file to free up physical RAM to guaranty VM01 reservation and admission control let VM01 boot ?

Thanks in advance !

[weinstein5]

Shares will not free memory to satisfy a reservation - total memory reserved is tabulated by adding the reservations set on the vm even if the vm is not using the reservation - also you need to understand how HA calculates available capacity - in regards to your example and HA - lets assume you have 16 VMs and only one has a reservation of 1 GB - HA caclulates the amount of memory needed based on the highest reservation of the VMs in the cluster so with only 1 VM with reservation the HA assumes that it will need 16 x 1 GB available after a host failure -

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[Junior_FR13]

Hi,

thanks a lot for the answer, but i don't know if i really understood : why the ha cluster will need 16x1GB in case of a host failure if there is only only 1 vm reservation ?

thanks in advance

[weinstein5]

It is the way HA calculates required resources for failover -

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[Junior_FR13]

Ok i think i understood : the HA calculate failover capacity by multiplicate the highest reservation by the total number of VM ?

[weinstein5 · Accepted solution]

exactly - this is true for memory and CPU

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