4cpus or 2 cpus

[tdubb123]

Does it make a big difference if a server has 4cpus or 2 cpus? I will end up using 2 more proc licenses for 4cpus hosts but are there any other advantahes or disadvantages going with 2 cpus vs 4?

[VMwareAndrew]

It will depend on the workload of your host.  You can have more VM's or larger VM's with more CPU's on your host.  Is that something you need now or in the future?

Remember you will have some CPU overhead to run ESXi, though not a lot.

[vThinkBeyondVM]

It is all depends on workload each VM is having & number of VMs you are going to place etc.

Ideally you will be allocating vCPUs to your VMs. hence it is better to understand vCPU and pCPU in detail.

Plz refer these great posts: 1. Virtual CPUs – The Overprovisioning Penalty of vCPU to pCPU ratios | ZDNet

2. Some thoughts about pCPU/vCPU | VirtualByte

3. What should be the ratio of physical CPUs to virtual CPUs in vmware. | LinkedIn

[jrmunday]

This is the "scale up" / "scale out" dilemma ... as as they previous posts allude to, it requires understanding of the workload.

I had this scenario for a MSSQL virtualisation project that I was working on and found the "sweet spot" for me was to deploy HP DL380p Gen 8 servers with 2x CPU's (each with 384GB RAM) ... since memory was a big consideration for me too, it meant that I could get more RAM into the cluster for SQL while maintaining the same number of number of vSphere licences.

Cheers,

Jon

[sph]

Generally 2-socket boxes have been significantly cheaper than 4-socket boxes and due to the increasing power in 2-socket hosts we’ve all but finished with deploying 4-socket machines except when specifically required.

Just an additional point to add, don’t forget the implications of application licensing when choosing specific processors, particularly with MSSQL which can be licensed by core as opposed to socket.  In this situation, a 12-core pCPU will have have 1.5 times the licensing cost of an 8-core pCPU, and yet, with its higher clock speed, the 8-core pCPU may significantly outperform a 12-core processor on a per-core basis.  This may free up budget for additional hosts.

You may find it useful to review the SPEC scores for the systems and configurations you are interested in at http://www.spec.org as an aid to your decision making.

As noted by the previous posters, knowing your workload is crucial, and taking into account your application as well as host licensing will assist you greatly to get the most value for money.

Simon