40 vcpu VM hardware requirements?

[lledarby]

Hi all,

Running a 15 node cluster with 2 socket/6 core blade servers.  I got a request for a 40 vCPU VM.  I'm having a brain fart here.  Do the Physical servers have to have more than 40 Cores to run this?  I always thought the root Resource Pool would share the CPU in the cluster to give the VM the 40 vCPU but my colleague thinks otherwise. 

We are running ESXi 5.1 Enterprise Plus.

[MKguy · Accepted solution]

One VM is only running on one physical host at any given time. This means a single VM can only use the resources provided by a single host. As one vCPU maps to one thread of a physical CPU, it doens't make any sense at all to provide a VM with more than 24 vCPUs in your environment (2x6 cores + HT which you should have enabled). I also think you can't even create a VM with more vCPUs than you have physical threads available in your single host.

The request for 40 vCPU seems obviously oversized and unaware of the infrastructure. I hope they have an extremely solid and objective explanation for this, which I guess they don't have at all.

Hell, even a physical recent Intel 2-socket, 8-cores +HT powerful server can't provide them with that much CPU resources.

[lledarby]

Thanks,

Unfortunately vendor is recommeding these specs for an Analytics app.  There are 4 socket 10 core Intel blades out there. ..

[MKguy]

Not the first time I've seen vendors pull out completely arbitrary resource "recommendations", just to either compense for poor application design or some ridiculous unrealistic worst-case peak workload. Unfortunately, people seem to expect magic words like "Database/SQL/Mailserver/CRM/Analytics/Business Intelligence/[insert buzzword here]" alone without any specific context as a free ticket to resource gluttony.

With a statement like that, I doubt they would even support virtualized platforms in the first place. Also imagine how much RAM and possibly IO you'd need to keep a system like that busy.

Yea, the blades are out there and will easily cost you around 30k a pop.

[lledarby]

Completely agree with you that these are over kill specs - 40vCPU and 256GB of RAM, however thats what IBM is telling the App owners.  At 4mil in software licensing I don't think they have an issue with spending 10% of that cost on Hardware.  What we will find is we have a lot of excess capacity to use for new servers.