Best option for many cors kVM

[Sakis]

Hi all,

Which option will be safer to run a kvm with many cores?

I have a 4 x E7-4850 host with total 80 cores. I have a need to run a 72 cores linux system in this host (I will keep 6 cores for ceph and proxmox)
What will be the best cpu conf for the vm?
Should i enable NUMA?
Should i choose a 1 socket 70 cores conf or 4 sockets 18 cores? Licencing is not a problem.
What is the safest cpu option? I currently run it with kvm64. When choosed host or qemu64 the vm didnt managed to boot.
My main concern is stability but performance is highly needed.

Thank you

 

[spirit]

>>Should i enable NUMA?
yes, you can enable it. It's improve memory access.

>>Should i choose a 1 socket 70 cores conf or 4 sockets 18 cores? Licencing is not a problem.
This is the same if you don't use numa.

If you use numa, try to have same number of socket than your host. (I'll try to map the guest cpus to the host cpu as much as possible, to optimize memory access)


>>What is the safest cpu option? I currently run it with kvm64. When choosed host or qemu64 the vm didnt managed to boot.

kvm64 is best if you have mixed intel/amd cluster.
In your case, you can choose ivybridge/haswell/.... ( E7-4850 v1 , v2 ,v3 ?)

 

[Sakis]

Thank you for your answer,

We are having various problems with cpu configuration. Guest (centos 6.5) cant see correctly the cpu no matter what we choose.
Its v1. I will try with bridge name option.

 

[adamb]

Thank you for your answer,

We are having various problems with cpu configuration. Guest (centos 6.5) cant see correctly the cpu no matter what we choose.
Its v1. I will try with bridge name option.

I can chime in on this one to degree. Honestly I don't know of many users running huge VM's other than myself and 1 or 2 others. We are currently running a single VM (CentOS6.6) with 46 cores and 768GB of ram. We have done this with small clusters now for a few years. No issues with booting for us. We use type host for cpu.