Let do a refresh. In vSphere 4, for Enterprise edition is entitled to 6 cores per physical processor per server. For Advanced/Enterprise Plus edition, is entitled to 12 cores per physical processor. As for the RAM limitation will be 256GB memory per host except Enterprise Plus which is unlimited.
An example would be follows:
1 server with 2 physical CPUs, each with 8 cores. This will require 2 x Enterprise Plus license.
If you apply 2 x Enterprise instead of Enterprise Plus license, only 6 cores per CPU will be used and 2 cores per CPU left idle.
Let's talk about vSphere 5 licensing. Before we begin, vSphere 5 have removed Advanced edition. A customers who is on Advanced Edition on vSphere 4 will be upgrade to vSphere 5 Enterprise.
vRAM entitlement is based on an edition per physical CPU (no more limitation of number of cores). It is based on vRAM allocated. So what is vRAM different from physical RAM?
vRAM actually define the virtual memory that is allocated to any VM that is powered on. But there are misconception here that most customer have.
If you have a server with 128GB of physical memory with 2 physical CPUs, do I purchase 128GB of vRAM? The answer is No and Yes. In a normal setup, we often set buffer of resources for HA. In such, this buffer does not have to take into consideration. Since allocated memory to a VM remain the same if HA kicked in due to host failure, you are not using twice as much the vRAM as the vRAM will be returned to the vRAM pool.
And Yes, if you have less physical RAM you can still overcommit your vRAM entitlement however this is not recommend. Explained in next consideration.
What if I need to increase the allocated vRAM to a VM once awhile? VMware will only measure the average vRAM allocation per year. In such, occasional increase or even creation of a VM for testing for a short period and later destroyed or power off will not bridge your entitlement as long in average/year allocation does not exceed. This is possible as the license does not have a hard restriction on the server even though you do not have enough vRAM entitlement you are still able to allocate more than you have. You will however see a warning when you overcommit your vRAM entitlement on vCenter and support will ask you to purchase more license when you log a call.
When planning your license, you do have to take note of the vRAM required minus the buffer used for HA where e..g N+1 is used. Of cause you can always buy additional license in the future when needed as well.
If HA was to kicked in when one host were to fail, the entitlement on the failed host will be available and shared by the remaining hosts. i.e. to say the total vRAM entitlement will be pool together and shared within the cluster. Provided that the editions are the same.
Taking the same example of the physical server as above:
1 server with 2 physical CPUs (cores is not a concern), 132GB physical RAM.
Since there are 2 physical CPUs, you would need 2 x any edition license.
Then we will take note of the vRAM now.
If you are on Standard license, you will be need 2 x Standard which entitles you to 32x2=64GB vRAM.
Say you intend to have 100GB of vRAM for use taking consideration for future VM requirement by leaving 32GB physical memory for HA. We will be short of 36GB vRAM. Then you will need to get extra 2 x Standard license to top up as 2x32GB is 64GB of vRAM which will cover the 36GB requirement. So now your entitlement is 128GB.
Say you are into Enterprise license, you will still need 2 x Enterprise Plus = 96 x 2=192GB of vRAM. In such, you have more than enough. In such, you can even increase the physical RAM without purchasing additional vRAM license.
Now you may ask why do I have to buy so many Standard from the example above? Can I just buy another edition to top up? The answer is Yes and No and is not a recommended practice. If a host is entitled to a different edition, the entitlement cannot be shared. In such, the host that is assigned to the different edition license will be standalone and its vRAM entitlement will not be pool together. Best practice is still to purchase the same edition whenever possible to avoid overheads on management of license.
What if I have a monster VM that requires more than 96GB of memory that Enterprise Plus entitles (96GB vRAM entitlement)?
If you are on Enterprise Plus, a VM can be allocate more than 96GB of vRAM without any penalty. Its license for each VM is 96GB vRAM or above. However 1 x such license would be used and if you need to power on more VMs on the same host, you would need more license as one complete 96GB vRAM license (Enterprise Plus) has been allocated to the monster VM.
If I need a VM to have more than 8 vCPU. Then you would can only use Enterprise Plus license. This is because, all editions maximum vCPU per VM is 8. For any VM which need more than 8 vCPU only Enterprise Plus would be meets the need.
What if you are using View won't I have to purchase lots of license?
Answer is No. For View, vRAM is unlimited license. It will be Desktop license which has unlimited vRAM entitlement.Your license for View will be base on per concurrent user connection. However per processor socket still applies that is if you have 2 sockets processor, you would need two desktop edition of license. However in a View license, you can have unlimited vSphere license i.e you can have many hosts to host the number of licensed concurrent users.
Note: View license can only host View servers components and desktop VMs and not allowed to host server workload.
Since the free Hypervisor allows 32GB of physical memory, then why should I buy any edition license of standard and below?
1. You enjoy the licensed features of HA, DRS etc. and managed by vCenter instead of multiple direct consoles login.
2. Free Hypervisor is entitled to 32GB physical memory and 32GB vRAM entitlement. That is, even if you have more physical memory it cannot be used. Or if you have less than 32GB physical memory, you only can only overcommit your vRAM to no more than 32GB.
IMPORTANT: Due to the different licensing entitlement for vRAM for Desktop and infrastructure, it is not allowed to host server workload on Desktop license.
I have the table of the license entitlement below:
|vSphere Enterprise Plus||96 GB||32|
|vSphere Enterprise||64 GB||8|
|vSphere Standard||32 GB||8|
|vSphere Essentials Plus||32 GB (Max 192GB)||8|
|vSphere Essentials||32 GB(Max 192GB)||8|
|vSphere Hypervisor Free Edition||32 GB (physical memory Entitlement and vRAM entitlement)||8|
Note: For Essential and Essential Plus, the maximum vRAM entitlement for each vCenter is 192GB as the maximum support total hosts not exceeding 3 hosts with no more than 2 pCPUs, it will results in 2 CPU x 3 hosts x 32GB each = 192GB. For these two editions, it is a hard enforcement unlike Standard, Enterprise and Enterprise Plus.
To summarize, cater your HA buffer on physical memory of your server and cater enough vRAM for scalability. Do the right sizing and not make life simple by sizing vRAM equal to physical memory. If your end user knows how vRAM works, you will be criticize.
Partner central license simulator:
vSphere 4 features
vSphere 5 features
vSphere 5.0 vRAM compliance and usage
Update 3: Add feature reference for vSphere 4 and 5 on different editions.
Update 2: Refine wording for easier understanding.
Update 1: vRAM entitlement restriction applies to Free Hypervisor.
Other related posts:
vSphere 5 vRAM Licensing
vSphere 5 ESXi 5 Installation
Upgrade vSphere vCenter 4.x to 5.0
Upgrade ESX/ESXi 4.x to ESXi 5.0 using Update Manager
Upgrade VMware Tools and virtual hardware with Update Manager