[SOLVED] Found significant performance difference between selecting CPU = host and CPU = x86-64-v2-AES

[muekno]

As I learned in another thread, for clustering and live migration CPU have to be the same and it was recomeded to use i.e. x86-64-v2-AES instead of host.

My server has CPU type 2, till now I used host, thats OK for me as I do not plan a cluster. But on customers site a cluster is planned, cpu type is an issue
.
While testing I installed a simple debian 12 textmode with CPU = x86-64-v2-AES and found update and install quite slow to previous experiance.
So I installed an identical system, cores, sockets, ram, storage, disk size etc. with CPU = host and update install etc. runs at least 5 times faster.
Could that be?

 

[shanreich]

Yes, since x86-64-v2-AES supports less flags than your host CPU the performance is expected to be worse. You could try and identify the set of flags that ALL CPUs in the planned cluster support and create a custom CPU model with those flags. That should then maximize the possible performance while retaining compatibility.

 

[muekno]

Thank you for fast response. Do I expect problems if all CPUs are same type i.e. type 2, got the number from here (https://github.com/HenrikBengtsson/x86-64-level/blob/develop/README.md) and I use host. And what is if I do waive live migration and just migrate and the start.?

Regards

Rainer

 

[shanreich]

Thank you for fast response. Do I expect problems if all CPUs are same type i.e. type 2, got the number from here (https://github.com/HenrikBengtsson/x86-64-level/blob/develop/README.md) and I use host. And what is if I do waive live migration and just migrate and the start.?

The probability for issues with the x86-64-v2-AES CPU type is a lot lower, not 0, but from our experience it usually works quite well.

If you do offline migration, then different CPU types should not be an issue, although Windows and some software is known to sometimes cause issues with suddenly encountering a different CPU - particularly when licenses and keys are tied to some kind of hardware key. You would have to try that for yourself with a test VM.

 

[muekno]

Thank you Stefan
Customers most VMs are Debian and SUSE SLES

Regards
Rainer