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Reducing windows server costs in a Vmware ESX cluster of 16 servers

Posted on 2009-05-09
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Last Modified: 2012-08-14
Hello,

we got a vmware cluster with 16 physical servers they are connected to virtual infrastructure with VMotion / DRS. All data is stored on a SAN.

Usually we use Debian Linux servers but we are about to migrate our windows servers to that cluster instead of buying new hardware for them.

My question is, is there a way to minimize the licensing costs for windows. I know there is the windows datacenter edition and it allows us to run unlimited servers on a single server (licensed per CPU) but with 16 * 4 CPUs (and more to come) we would feel "a little bit overlicensed" to deploy our 12 (!!) windows servers (win 2k3 standard using 1 cpu) in that cluster.

So is there a way to tell vmware vmotion to move those windows servers just around let's say 3 servers licensed with 4 cpu datacenter editions?  Or how should we proceed here?

Tolomir
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Question by:Tolomir
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12 Comments
 
LVL 6

Assisted Solution

by:davismisbehavis
davismisbehavis earned 100 total points
ID: 24345316
I'm presuming that when you talk about vmotion,  you mean DRS movement of these windows boxes around the 16 hosts in the cluster. The problem is that you can't really associate VM's with hosts unless you use CPU affinity and this then ties you to a single host and unfortunately a 1:1 assocation with the CPU which is not the best for CPU scheduling at the vmkernel level.

What you could do though is create 3 Dummy VM's (no disks, min memory, etc) on the 3 hosts you have licensed for windows data centre,  create them on local disk as opposed to on the SAN that way they can't be vmotioned.  Create an DRS affinity between 4 of your windows VM's and the dummy VM that is stored locally and repeat this on all 3 hosts.  These machines unfortunately will no longer vmotion as part of DRS but you have manually load balanced them already across the 3 hosts.  Other machines not associated with the dummy VM's on the same hosts will vmotion off if there is resource contention so that should stop any issues  and ensure that your windows servers don't suffer.

If you've got HA on your cluster then you should be protected for any host failure scenario.  This should allow you to confine everything to 3 hosts and keep the costs down,  hope this helps.

www.virtualpro.co.uk 
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Accepted Solution

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SPremeau earned 250 total points
ID: 24345540
It may be that you've reached the point of your VMware implementation that you need to break your machines into separate clusters.

The proposed solution above will work without breaking your cluster, but does have some limits.  Depending on your scenario, it may be that you can separate your ESX machines into a 3 machine cluster and a 13 machine cluster (depending on how it works, you may shrink your remaining cluster too).

It is carving up your resources a bit, but the only limit in this case is that the DRS wouldn't automatically move machines between the group of 3 and 13 (which is what you want for windows).  However, you still would be able to manually vmotion things between the clusters if you need to.
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LVL 27

Author Comment

by:Tolomir
ID: 24350167
Thank you for your suggestions:

davismisbehavis: Yes you were right with DRS movement. I think it should also work to create a snapshot, this (as our admin told me) makes it impossible to move) - Still how do I create this DRS affinity,. Can I do it with VI client?

SPremeau: How can I split the cluster? The problem with this solution is we really got just 12 windows servers all of them just tomcat application servers. So no big exchange server or such. It might be sufficient to use 2 esx servers then. There goes DRS down the drain....

Bonus question to both of you: Would this be sufficient for Microsoft to "allow" us to just license 2 or 3 esx servers for windows?

Tolomir
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LVL 35

Expert Comment

by:ShineOn
ID: 24350944
Windows Server Enterprise licensing allows you to have up to 4 virtualized guests per physical host per license.

If all of your existing servers are standard and not enterprise you are limited to one instance on one host per license. Caveat:  If any of them are OEM licenses, the guests can't transfer to another host via VMotion, but if they're volume licenses (open or otherwise) they can transfer via VMotion - but you need to have a license on both/all of the hosts that could host a given guest.

To minimize your licensing costs and have the guests transferrable using VMotion, you need to go for at minimum three, more to have installed licenses on additional hosts that would particiate in VMotion, licenses for Windows Server Enterprise, preferably under some sort of volume licensing, with no more than four Windows instances per VMware host that will be participate in transfer of guests amongst them using VMotion.  If that makes sense... ;)
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LVL 27

Author Comment

by:Tolomir
ID: 24351438
Hello Shineon, i think you are missing the peak usage problem here. Sometimes we have to patch these esx servers. Then we must move all machines from that server to another node.Last week we even had to disable 12 of our 16 servers sue to a power supply issue. You can assume that in such a case all windows servers would be moved to a single esx server. Datacenter license is the only possible way.

Tolomir
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LVL 19

Expert Comment

by:vmwarun - Arun
ID: 24352352
The point to note is a Windows Server 2003 Datacenter Edition License provides you the ability to install as many number of 2003 VMs per single host.

If you need to use vMotion, then you would need as many number of Datacenter Edition Licenses equal to the number of Hosts in a DRS Cluster.
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LVL 19

Assisted Solution

by:vmwarun - Arun
vmwarun - Arun earned 50 total points
ID: 24352370
DRS Affinity per VM can be configured by right clicking on the DRS Cluster properties by using VI Client and connecting it to VirtualCenter Server.

But setting CPU affinity will disallow the use of VMotion and HA.
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LVL 27

Author Comment

by:Tolomir
ID: 24352659
So activating CPU affinity counts for all virtual systems, not just those windows servers?

So I really had to setup a separate cluster for windows (for 12 servers...)?

 


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LVL 27

Author Comment

by:Tolomir
ID: 24352835
ok seems like I found it.

So what do I have to do during patching, remove this setting - move machines to another (licensed) server then redeploy affinity?





vmware-drs.jpg
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LVL 35

Assisted Solution

by:ShineOn
ShineOn earned 100 total points
ID: 24357360
Tolomir, if Datacenter is the only possible way, then why even ask how to reduce Windows licensing costs?  The ensuing discussions don't even touch on that core issue of your Question, IMHO, other than that you need to limit the number of hosts that can host an instance... and in your scenario of 12 of 16 being down (and there'd be no predictable pattern as to which they would be) then limiting the number of hosts that could potentially host an instance isn't necessarily what you're looking for - or is it?

You are aware that Microsoft volume licensing does allow you to reassign licenses, correct?

http://download.microsoft.com/download/F/C/A/FCAB58A9-CCAD-4E0A-A673-88A5EE74E2CC/Windows_Server_2008_Virtual_Tech-VL_Brief-Jan_09.docx
http://download.microsoft.com/download/6/9/5/695BA00D-C790-4C90-813A-F10539D97991/Application_Server_License_Mobility_VL_Brief_Nov_2008.docx

Using the Windows Server Virtualization Calculator: http://www.microsoft.com/windowsserver2003/howtobuy/licensing/calculator.mspx

If you take a worst-case scenario, based on 16 4-processor servers, with up to 12 instances on each,  Microsoft would have you pay (retail) $112,032 for Enterprise licensing vs $152,384 for Datacenter, so tell me, how is Enterprise not a viable option?  Even if you buy 3 licenses for each host machine, you still come out cheaper than Datacenter.  If you bump your server farm up to 8-processor servers, the Enterprise licensing cost remains the same but your Datacenter bill doubles to over $300K.

If you had dual-processor or uniprocessor hosts, Datacenter would be cheaper than Enterprise, because Enterprise isn't licensed by processor.

The only way to reduce the impact of using Datacenter is to reduce the size of your farm, as the others are saying.  If you want to leave your server farm intact as one big vmware cluster, you would be better off with Enterprise.

Again, that's worst-case scenario.  Given that you can move licenses from one host to another (you just can't move them very frequently) then you could have fewer than 3 Enterprise per server and still be able to handle a disaster situation like the one you shared wiith us.

If you were planning to limit the number of servers with licenses installed, to, say, 3 as has been suggested, then you still save 7 grand using Enterprise over Datacenter.  
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LVL 27

Author Comment

by:Tolomir
ID: 24358117
Shineon, right now we are hosting about 300 (web) servers, we are about to double that in two or three years. This also includes windows servers.

I went through that calc and I'm aware of windows peak usage and move license each 90 days or due to hardware crash. Then we even had the argument that there might be a different ruling in the EU in contrast to the US.

We are a (web) hosting service provider for public service and what bugs us most is that we cannot simply move all servers onto that vmware cluster to move them around as needed without taking care of proper HARDWARE licensing.

You made all great (technical) suggestions, I keep it open until we talk to our IBM partner in that matter and keep you updated.

Tolomir
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LVL 27

Author Closing Comment

by:Tolomir
ID: 31579814
Thank you very much for the suggestions.

This is from the vmware expert: Most companies ignore the problem, license their server as if they were physical and he recommends to split the cluster and put data center on each of the small cluster servers.

The split can be done via VI client so we will consider that option.
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