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VM with 20GB of memory with 8cores?

So,

I have a VM on ESXi 6.5 with 20Gb of memory but 8 cores as well. I think that's a bit odd but I'm wondering if it would in fact cause any issues or performance impact. Essentially I figured it'd be something to do with the vNUMA and the pNUMA and how it manages across the two.

I know that 6.5 has improved the vNUMA considerably, so I'm wondering if this is still an issue, if so can you provide any documentation?

Thanks
Alex

Ben Personick (Previously QCubed)

Numa scheduling a large number of cores on a VM isn't in and of itself an issue.

To determine if there is a problem with a VM of 8 cores requires knowing:

A) The underlying physical hardware's total number of virtual cores. (Virtual Cores = 1x or 2x the value of Physical cores (1x is Hyper threading is disabled, 2x if HT is enabled) (physical = total cores across all CPUs on the system)
B) The mix of additional VMs on the system, their number of CPUs, and average load.

Alex

ASKER

It's a 24 core server with 256GB of memory

So 48 logical Processors.

Thanks
Alex

Andrew Hancock (VMware vExpert PRO / EE Fellow/British Beekeeper)

ESXi 6.5 is better now, providing you have assigned CORES (for your vCPUs). (e.g. not sockets as per original thoughts pre 6.5)

see here

https://www.opvizor.com/decoupling-of-cores-per-socket-from-virtual-numa-topology-in-vsphere-6-5

https://blogs.virtualmaestro.in/2018/05/vnuma-vmware-vsphere-65.html

https://blogs.vmware.com/performance/2017/03/virtual-machine-vcpu-and-vnuma-rightsizing-rules-of-thumb.html

Alex

ASKER

2 sockets and 4 cores on each socket have been assigned.

ASKER CERTIFIED SOLUTION

Andrew Hancock (VMware vExpert PRO / EE Fellow/British Beekeeper)

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Alex

ASKER

Perfect, so stick with solid cores and then this should in fact improve performance going forward.

Excellent, that explains a lot, as for the 20GB of memory, that wouldn't cause any performance issues given the lack of cores and the large quantity of memory as it did before?

Thanks
Alex

Alex

ASKER

Thank you both gentlemen, always a pleasure learning from the pros :-)

Ben Personick (Previously QCubed)

Hey Alex, Glad to help :)