One of my friends recently emailed me to clarify a point on potential implication of Microsoft Server Licensing on VMware, in perticular with regards to VMotioning (moving running VM's amongst different physical "ESX" servers). He was notified by their software partner during a recent audit that either they need to starting buying windows data centre licenses to cover all the ESX server CPUs in order to continue free DRS initiated (or Otherwise) VMotion, or turn off VMotion alltogether.
So I thought I'd share my reply to him with all of you as this seems to be an area that is still either not very clear amongst lot of folks OR often, people simply choose to ignore alltogether (arguably, due understandable reasons). I've obviously modified some lines to remove the identity of my friend...etc but the message remains intact....!!
NB: Please note that this info only applies to server virtualisation and NOT VDI
Windows Licensing & VMware
Unfortunately, the common assessment that Windows Datacentre license is the most practical method to license your VMs within an ESX cluster is the correct one if you want the VMs to freely move in between physical ESX hosts via VMotion as a part of DRS initiated VMotion or otherwise (i.e. Administrative VMotion for maintenance tasks).
In order to understand why, you first need to understand the MS server licensing limitations. Usually, all windows server licenses are tied to the underlying physical hardware. This is still same even if that server is a VM, in which case the VM's OS license is tied to the ESX servers hardware, usually the ESX server where the VM ware created & build with that Windows Server OS. So, when you look at VMotioning that VM off of that ESX server to another, the following limitations apply.
- If its an OEM Windows Server license, the OS license is tied to the original ESX server hardware (regardless of whether its STD, Ent or DC license) and is never moveble to another hardware through VMotion or any other method. So No VMotioning allowed there.
- If its bought though a Volume Licensing program, (Regardless of the license type - STD, ENT and DC), it can be reassigned to another physical hardware (i.e. the VM can be VMotioned from one ESX host to another) ONLY every 90 days through VMotion or other methods. It however permits you move it from one ESX server to nother in the event of a hardware failure without being subjected to this 90 day rule. (So HA initiated VM restart on another server due to hardware failures are permitted)
It only allows to run 1 instance of that VM on a specific set of underlying hardware. i.e. If the VM was licensed on ESX01, it is only licensed to run on that server's hardware. If the VM is to run on ESX02 after being VMotioned, you need to have another Widows server 2008 STD license to cover that.
With Windows 2008 ENTERPRISE
With Windows 2008 Data Center
- Total costs under Widows Standard licensing = 600 x 32 x 4 = £76,800.00
- Total costs under Widows Enterprise licensing = 1900 x 8 x 4 = £60,800.00
- Total costs under Widows Data Centre licensing = 2000 x 4 x 4 = £32,000.00
Clearly the Windows Data Center license turns out to be the cheapest in comparison.