Threshold point at which VMs are throttled back

[HippoUK]

Hi all

Assuming that VMs are configured with shares rather than reserved resources.

At which point do the "shares" kick in? My assumption being is that this is internally calculated by the numbers of VMs configured and the physical resources?

Also are shares a timed based algorithm like network QoS or will the minimums be retained throughout until overall utilisation drops allowing more resources to be allocated back to the resource pool?

Any help gratefully received

Ian

[MKguy]

At which point do the "shares" kick in? My assumption being is that  this is internally calculated by the numbers of VMs configured and the  physical resources?

Also  are shares a timed based algorithm like network QoS or will the  minimums be retained throughout until overall utilisation drops allowing  more resources to be allocated back to the resource pool?

Shares only kick in when there is resource contention and are purely applied proportionally to the siblings shares value on the same level. If your VMs real demand is lower than the resources available (which I hope will be the case 99% of the time), there is no need to prioritize something.

This is very important to keep in mind and one of the big advantages of shares as opposed to hard limits/reservations, as it makes your resource usage a lot more dynamic and  effective.

I recommend reading the Resource Management Guide which explains this in detail and/or the HA and DRS Deepdive book:

http://pubs.vmware.com/vsphere-50/topic/com.vmware.ICbase/PDF/vsphere-esxi-vcenter-server-501-resour...

http://frankdenneman.nl/2012/08/vsphere-5-1-clustering-deepdive-available/

[HippoUK]

Thanks for the reply and previously I have read the Resource Management document which makes sense - however a customer server is showing that the VMs are working with the "worse case" when the VMware server itself is operating at below 50% utilisation for CPU, memory etc

.

Other VMs are hardly being used so resources which ever way you look at it, is not an issue

Doesnt make sense to me, there must be some kind of internal threshold