Question about Resource Pools

[dbutch1976]

Hi guys,

I have been studying resource pools in my home lab in preparation for the VCP 4 exam.  I have read the managing resource pools pdf:

http://www.vmware.com/pdf/vsphere4/r40/vsp_40_resource_mgmt.pdf

I'm a little confused, hopefully someone can clear this up for me.  A practice question states that a virtual machine will always fail to power on if the virtual machine's reservation cannot be guaranteed, however in the KB article below it states that admission control can be disabled.

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=100700...

Therefore it is my understanding that not being able to guarantee the machine's reservation does not necessarily prevent the machine from being turned on because admission control can be disabled.  Is this correct?

[scott28tt · Accepted solution]

Reservations must be guaranteed as per your comment. That's related to resource pools.

Admission control is related specifically to HA, and is about ensuring that a VM can only be powered on if it's availability can be guaranteed according to the admission control policy. HA can use VM reservations plus memory overhead as part of those calculations.

Disabling admission control would allow you to power on a VM even when the availability of that VM could not be guaranteed by HA, which is a different situation from when the VM lives in a resource pool.

Just because you're using HA doesn't necessarily mean you're using resource pools or DRS

Scott.

[dbutch1976]

Thanks Scott, I found that very confusing and I think you've cleared it up.

[scott28tt]

If you really want to get your head around HA and DRS, check out Duncan Epping's blog: http://www.yellow-bricks.com

Scott.