What does 4-way, 8-way mean?

[SteveDavidson]

In the near future, I will be implementing a couple of x3550 dual cpu, quad core machines for a virtualization project. This is a term that I have not been able to define. Here is a quote from the book I am reading "Tuning IBM System x Servers for Performance"

"There are a number of different methods to use to calculate the number of ESX

systems you will need. Here are two of the more popular methods.

Method 1

The easiest rule of thumb is 4 to 5 virtual CPUs per physical CPU. This would

result in 16 to 20 virtual machines per 4-way host or 32 to 40 per 8-way host,

assuming that all were one vCPU virtual machine and had low-to-moderate

workloads."

So when they say 4-way host, are they saying the same thing as quad core? And 8-way would be dual quad core? So the rule would be 4 to 5 virtual cpus per core?

[J1mbo]

Indeed - about 5 vCPUs per core. If you use vSMP this will be reduced significantly.

Please award points to any useful answer.

[dnetz]

4-way and 8-way refers to the number of CPU sockets in a server. However, this rule of thumb assumes 1 core per socket, as explained three paragraphs down in the text.

===

If you find this information useful, please award points for "correct" or "helpful".

[RParker]

4-way and 8-way usually refers to the number of CPU sockets in a server. I've never heard it being used for the number of cores

Incorrect, it's ALWAYS been the CORES not SOCKET. Maybe people use it interchangeable, but its the number of cores. Maybe it's been around before core, and they refer to the sockets in that fashion but they are referring to the actually number of processors assigned, because we use the same terminology for VM's, 2-way 4-way and we certainly aren't referring to the socket.

[dnetz]

It seems they do use it interchangeably, though I would agree that using it for cores makes more sense.

===

If you find this information useful, please award points for "correct" or "helpful".

[SteveDavidson]

Ok. So I am getting the general idea. With one IBM x3550 m2, dual quad core 2.93 GHz cpus, I could potentially get anywhare from 4 * 8 (32) to 10 to 12 * 8 (80-96) virtual machines, depending on other resources available. Thanks! Can I award points to everyone?

[RParker]

So when they say 4-way host, are they saying the same thing as quad core? And 8-way would be dual quad core? So the rule would be 4 to 5 virtual cpus per core?

yes but you are reading outdated material. The NEW ratio of VM's to host is 6 or 8 per core (with ESX 4.0). If you have Nehalem, or the new Intel 55xx series with hyperthread / turbo boost that is more like 10 or 12 VM per core. but yes an 8-way would mean 8 TOTAL physical cores (on including hyperthreads).

[TomHowarth]

4-way relates to the number of Processors in the server as 4-way is a quad CPU box and an 8-way is an 8 CPU server. so in the case of this RedBook they are assuming single Core CPUs, as if they were considering 2-core or 4 core the guest density would be 32-40 and 64 to 80 respectively

If you found this or any other answer useful please consider the use of the Helpful or correct buttons to award points

Tom Howarth VCP / vExpert

VMware Communities User Moderator

Blog: www.planetvm.net

Contributing author on "[VMware vSphere and Virtual Infrastructure Security: Securing ESX and the Virtual Environment|http://www.amazon.co.uk/VMware-VSphere-Virtual-Infrastructure-Security/dp/0137158009/ref=sr_1_1?ie=UTF8&s=books&qid=1256146240&sr=1-1]”.