Comments on: Resource Pools and Shares

By: Tarun Lohumi

Tarun Lohumi — Thu, 25 Feb 2010 04:27:40 +0000

Hey Duncan,

Thanks for the nice article.

So, I was thinking it’s all about the following number:

Shares/# of VM’s

Show for RP-01 this number comes out to be 2000/6 = 333
& for RP-02 this number would be 1000/3 = 333

So we can safely say that when all VM’s are contending all of them would get exactly the same amount of resources.

The higher that number is, higher is the resources per VM.

Am I over simplifying things?

By: M-A

M-A — Thu, 18 Feb 2010 10:03:06 +0000

The conclusion I come to from this discussion is.
1. Most of use incorrectly configured resource pools possibly to the detriment of our guests performance.
2. There is no point creating resource pools in most environments unless you are going to monitor the number of guests in them and adjust the shares accordingly (and/or unless your using them for security reasons)
3. Given the fact that most people don’t get this right Resource pools are fundamentally flawed by DESIGN. Good one VMWare.
4. What we want from VMware is a resource pool solution designed so it allows us to effectively apply shares to a guest not a pool. I guess you could say something of a policy type solution. Eg.Put the guest into the resource pool and it inherits the pool settings rather than shares the pool settings.
Again may I say “GOOD ONE VMWARE. GREAT DESIGN!”

Again may I say “GOOD ONE VMWARE. GREAT DESIGN!”

Lets all put this one to VMWare as a feature request.

By: N-A

N-A — Mon, 18 Jan 2010 03:42:33 +0000

Excellent post. We have this same problem in our environment and are getting ready to try and redesign our resource pools because of it.

Duncan, would just creating more ‘normal priority’ resource pools be a viable fix for this? We have no chargeback in our environment and we really have no reason to set resource pools to anything other than ‘high’, ‘medium’ or ‘low’. We like them divided in this way but want to ensure the problem you note in this post doesn’t happen. One way of doing this seems to be simply creating more “normal priority” pools and dividing the “normal priority” vm’s among those pools. Thoughts?

By: Duncan

Duncan — Sun, 20 Dec 2009 09:58:01 +0000

That still depends on the amount of VMs in the Low Priority Pool vs the amount of VMs in the Medium Priority pool. The High Priority Pool will get more resources indeed. tough question, had me thinking for a while.

By: Eric Moriarty

Eric Moriarty — Wed, 25 Nov 2009 23:50:52 +0000

With regards to Chris R.’s comment. This seems logical to me, except that I wouldn’t set shares at all. If you have:

High Priority VMs RP
|- Medium Priority VMs RP (A nested Pool within High Priority)
|- Low Priority VMs RP (A nested Pool within Medium Priority)

Without any shares set, would this not achieve the desired result, sort of. If you had 8Vms in High and 8VMs in Medium nested pool, then in a contensious situation, would the High Priority VMs get way more priority than the VMs within the Medium priority, and thusly the medium prioirty VMs get way more resources than the VMs in the low priority pool?

By: daniel

daniel — Mon, 23 Nov 2009 15:09:29 +0000

Interesting indeed. Is there an easy way to accomplish what people (me including..) think they’re getting with three resource pools set to high, low and normal shares? It would be nice to atleast seperate test machines from production without having to set individual VM resources.

By: Anton Zhbankov

Anton Zhbankov — Tue, 17 Nov 2009 08:36:08 +0000

Duncan, CPU and Memory shares are simple to understand.

But what about Disk shares – what exactly is measured? IOPS, bandwidth? I.e. if I have VM generating enormous amount of short operations how can I set disk IO limit for IT so it won’t affect other VMs?

By: Duncan

Duncan — Tue, 17 Nov 2009 07:44:44 +0000

Correct,

another option is to leave shares alone

By: Vincent

Vincent — Tue, 17 Nov 2009 06:43:05 +0000

My conclusion after reading your article: Recount the vm’s in the Resource Pools in a HA-cluster on separated times and reconfigure your shares if necessary. Is this a correct conclusion?

By: AJ

AJ — Tue, 17 Nov 2009 02:11:36 +0000

I was looking at my customer’s environment today and they are sort of mixed. They have multiple clusters but all configured with High and Low resource pools. One pool for production(high shares), the other for Staging(integration; low shares). A couple of their clusters they have way more Production VMs than they do Staging VMs, so they could run into the above scenario if the VMs start to contend for resources. The other clusters are fairly balanced so the pools should work fairly efficiently. On the unbalanced clusters, my guess is I could increase the share amount for the Production cluster so that it is relatively larger than the Staging pool. For example, if the pools were originally a 4:1 ratio(High:Low), I could increase the custom share and make it say a 8:1 ratio. That way, the Production pool would get a higher overall percentage of the available resources. If my thinking is correct.