I was on a customer site today and was discussing the new HP Proliant 960 G7 server, when the conversation veered towards ESXi and vRAM licensing. it quickly became apparent that my client was labouring under a misinterpretation, so I had to explain how vRAM worked. I had thought that these issues had gone and everybody understood vRAM and the FUD that other vendors out about during the VMware vSphere 5.0 launch had been put to bed but it appears not. so with you further ado here is a brief overview of vRAM and its features per vSphere edition.
With the release of vSphere 5.0 VMware changed the licensing model from processor based with a Core count limitation to a processor based and vRAM limitation. so what exactly is vRAM? vRAM is a set about of physical ram that is licensed per processor this number varies from edition to edition, see the table below for full details of what vRAM count is defined per differing edition.
|vSphere Enterprise+||96 GB|
|vSphere Enterprise||64 GB|
|vSphere Standard||32 GB|
|vSphere Essentials+||32 GB|
|vSphere Essentials||32 GB|
|Free vSphere Hypervisor||32 GB (1)|
(1) relates to maximum memory allowed in physical host server and is not processor bound, i.e. 1pCPU 32GB Memory 2pCPU still 32GB Memory.
What this means with the exception of the Free vSphere Hypervisor is that each pCPU has an amount of free vRAM entitlement. now remember when this was released the majority of Hosts were running between 32 and 64 GB of RAM and environments were starting to move to 128 and 256 GB of RAM.
Also the vast majority of vSphere licenses out in the wild are (from my experience) Enterprise Plus.
so lets to a little bit of maths.
|Edition||Number of CPU||Total vRAM per Edition|
|Essentials & Essentials+||1||32GB (1)|
|Essentials & Essentials+||2||64GB (1)|
|Essentials & Essentials+||4||128GB (1)|
Essentials & Essentials+
|Free VMware Hypervisor||1||32GB|
|Free VMware Hypervisor||2||32GB|
|Free VMware Hypervisor||4||32GB|
|Free VMware Hypervisor||8||32GB|
(1) There is a Soft cap of 192GB of vRAM entitlement for the Essentials and Essentials + editions, now this can be bypassed but you will be in breach of your EULA for the edition and there is nothing to say that VMware will not patch the Soft limit to a Hard Limit and then you will be in a position where you cannot start VM’s. So basically don’t do it
So at the time of the license change (yes I am malarky when it was first introduced) the numbers were more than adequate for the size of the Hosts that were coming into service and for those that were 1-1/1/2 yrs ahead in the pipeline.
All that sounds pretty nifty but remember that VMware introduced the MONSTER vm with vSphere 5 this is a 32 virtual CPUs and one terabyte of virtual RAM beast of a Guest.
so if I created 32vCPU 1024GB beast of a machine that would cost me 10.6 licenses of Enterprise Plus in vRAM alone, well no.
VMware also capped the amount of vRAM per VM to 96GB
The following table from the Rethink IT explains it all.
|Customer feedback||Changes to the vSphere 5 licensing model||Impact|
|1. Affects only a small percentage of customers today, but customers are concerned about their future-looking business cases based on new powerful hardware capabilities||Substantially raise the vRAM entitlements per vSphere edition from 48/32/24/24/24 GB to 96/64/32/32/32 GB||With these increased vRAM entitlements, hardly any customer will be impacted by higher licensing costs upon upgrading to vSphere 5|
|2. Introduces additional hesitation for virtualizing business critical apps||Cap the amount of vRAM counted per VM at 96GB[i]||No application, doesn’t matter how big, will require more than one vSphere (Ent+) license to be virtualized|
|3. Penalizes short lived usage “spikes” in dev & test, and transient VMs||Calculate a 12 month average of consumed vRAM rather than a high water mark||Short lived “spikes” will increase the 12 month average a little but a customer will not be required to pay for them in perpetuity|
Now all this was well and good when Host machines were containing a maximum of 256GB of RAM but HP now has the Proliant 980 that can contain a maximum of 4TB of RAM perhaps it is time for VMware to revisit the vRAM maximums again. So this is a great box if you want to run Monster VM’s but from a licensing perspective, a nightmare for most normal workloads of say 4 to 8 GB of assigned memory.
Now I know that very few if any will use these beasts as Virtualisation host. but remember what is top of the range today, eventually becomes entry level. and Hosts with 512GB of Physical Ram are starting to get common place.
Food for thought.