Understanding Resource Shares

[aetius1980]

Hi,

I have a cluster of 15 ESXi 5.1 hosts configured without DRS and I'm trying to understand the shares values configured by a previous administrator:

I thought typically shares had a value of low, medium or high (or custom) and that the % of resource is equal to the number of shares divided by the number of vms in the low, medium or high pool. What I'm not sure about is how to calculate total shares, the % of shares and worst case allocation - mhz. The figures below don't quite make sense and I'd be grateful if someone could explain

thanks

[Wh33ly]

Here are some articles which will explain the use of shares

http://pubs.vmware.com/vsphere-51/topic/com.vmware.ICbase/PDF/vsphere-esxi-vcenter-server-51-resource-management-guide.p…

Page 11

https://www.vmware.com/files/pdf/techpaper/VMware-vSphere-CPU-Sched-Perf.pdf

Page 19

Hope this will give you a good start about shares

[aetius1980]

wh33ly,

Thanks for the tip. So, from reading, am I right in thinking the total number of shares in my system is the combined value of the shares value as shown in the graphic and that 8000 shares at a high share priority equates to 1% of share value? Would 8000 shares at normal priority equate to 0.5%?

Also, I'm not using resource pools, therefore does it matter how many VMs I assign to a specific high share priority? With resource pools, my understanding is that the share value is per vm in the specific resource pool, so if you have high, medium and low resource pools you would need to balance the vms in the pools to maintain per vm share allocation

[DanielOprea]

Hello,

Look at these other links for you to understand better.

http://www.yellow-bricks.com/2009/11/13/resource-pools-and-shares/

VMware vSphere Resource Management Configuration Basics

http://vmtoday.com/2012/03/vmware-vsphere-resource-pools-resource-allocation-revisited/

[Vikas Shitole]

Hi aetius1980,

Direct answer to your queries:

1. how to calculate total shares:

Sum of all the shares values allocated to each VM. In you case, Sum (8000+16000+4000+1000+.........) for all the VMs.

2. the % of shares:

Say Total shares are 12000 and VM1 has share value 1000.

Then % shares is : 1000x100/12000 =aprox. 8 %.

3. worst case allocation - mhz:

:The amount of (CPU or memory) resource that is allocated to the virtual machine based on user-configured resource allocation policies (for example, reservation, shares and limit), and with the assumption that all virtual machines in the cluster consume their full amount of allocated resources. The values for this field must be updated manually by pressing the F5 key. )

Refer:VMware vSphere 4 - ESX and vCenter Server

I am still investigating how it is calculated.

4. Would 8000 shares at normal priority equate to 0.5%?

No. It will not be 0.5%. still it would be 1%

I tested this in my environment with smaller setup (3 hosts and 2 VMs each with same configuration), for % share calculation, VMware has just considered sum of shares (not the priority).

In your case, we can see 8000-high=1% & even 8000-normal also =1%. Hence priority is not considered. This needs more investigation, I will come back to you.

My observation:

1. share values changes with different capacity host.

ex. In my case

H1 has  8 CPUs x 2.127 GHz CPU core (from host summary page) : Normal CPU share value was "1000": Hence all the VMs on this host will get share values wrt 1000. (In ratio 4:2:1)

H2 has 8 CPUs x 2.393 GHz CPU core: Normal CPU share value was "2000":Hence all the VMs on this host will get share values wrt 2000. (In 4:2:1)

Overall above observation shows that, as per UI : shares values are important than priority itself if the cluster is having hosts with different capacity but still this needs to be investigated and clarified. 

I will be back on further investigation.