dell r900 with 24 cores

[tdubb123]

I have a cluster with some dell r900s, 4 cpus, 6 cores per cpu. 96gb ram

how many vms can i assign to it if each vm has 2 vpus and 4 gb ram?

what is the ratio for the virtual cpus to the physical cores?

[Mouhamad]

Virtual CPUs per core 25 (http://www.vmware.com/pdf/vsphere5/r50/vsphere-50-configuration-maximums.pdf page 2)

24 cores x 25 vCPUs = 600 vCPUs (300 VM with 2 vCPUs)

As for the RAMs, keep 8 GB free for the hypervisor and the VMs overhead which leaves you with 88 GB

88 GB / 4 GB per VM = 22 VMs.

So you can easily run 22 VMs on this VM.

[mcowger]

In all liklihood, your VMs will probably NOT use all their memory, so 22 VMs should be a lower bound.  You are likely to be able to fit 40+

[Mouhamad]

I also suggest you increase the number of memory or decrease the number of CPU sockets or cores.

[Mouhamad]

Yea I totally agree, but again it depends on the OS you are running.

I'm facing issues with Windows 2008 Server 64 Bit, it is eating the whole 4 GB most of the time, and I really feel like I dont want to overcommit my physical memory. However, memory sharing, ballooning are really great.

[Nikhil_Patwa]

Hello,

Can you be more specific as to how many dell r900 do you have in your cluster. Moreover the specification you provided is for each dell r900 server correct.

The number of VMs per ESXi host with each VM having 2 vCPU and 4GB RAM can be varying and depending on the following configurations

1. Resource pools

2. Memory allocations

3. CPU allocations

4. Shares

5. Limits

I have a similar server dell T710 with 96GB RAM and am able to run 30 VMs with different RAM and vCPU allocations and still I have 40% RAM and 45% CPU free.

There is no fixed allocations of physical resources to VM and thus you can run more and more VMs as long as you dn not exhaust your resources but you can allocate memory, CPU, limits and shares to specific VMs or resource pools.

Theoratically you can have atleast 24 VMs running in each one of your Dell r900 ESXi servers (96GB RAM / 4 = 24)

WIth the new version of ESXi 5.0 VMware has come up with vRAM entitlements per license and depending on your license type you are allowed to allocate that much RAM only to VM and if you exceed the VMs will not power on.

Hope this information is helpful

Nikhil

[tdubb123]

its jus ta 2 node cluster. 2 R900 with 96gb ram. 4 cpus 6 cores/cpu

I am running mostly xp vms on it. with 2 cpus and 4 gb ram.

these vms frequently run jobs causing very high cpu usage. the physical cpu usage on both hosts can go as high as 90-95%

so far I have about 20 vms spread across both hosts.

a few 2008 vms but they are not using much.

so i have 48 cores in the cluster

is there a formula to calculate max vms on this cluster with 2 cpus each?

I am using single core for the vms. just 2 vpus

[Mouhamad]

As highlited in my post, maximum limitation per CPU is 300 VMs if each has 2 vCPUs.

In terms of memory, it's up to the VMs requirements and how heavy is this VM. 

[Nikhil_Patwa]

Why choose XP any particular reason? can the same jobs be run on server operating system, check out the performance with W2K3 VM

Ensure all your VMs are installed with VMware tools because I have seen VMs without VMware tools tend to eat up resources especially CPU

Nikhil