Exchange Environment - 4 vcpu faster than 10?

[cm350]

Hi all,

Sorry for the broken English, my native language is Dutch. I am from Belgium.

I assume this question was asked before but I am using the wrong keywords in the search.

We have on our Production Server (Proxmox 3.3-5 - 2x Intel Xeon E5-2650) a exchange environment.

5 x Windows Server 2012R2

1x Domain Controller (4 vcpu - 4GB ram - works perfectly)
1x Exchange with Client Access role (4 vcpu - 8GB ram - works perfectly)
1x Control Panel server (4 vcpu - 4GB ram - works perfetly)
2x Exchange with Mailbox role (4 vcpu - 16GB ram)

We recently had our share of iSCSI problems which gave us a corrupt Mailbox Database.

So we wanted to boost the cpu power on one of the Mailbox Database server to 10vcpu.

But to our surprise 10vcpu is actually slower than 4vcpu.

I checked it on a clean virtual server with prime95 and can proof that 4cores are faster punching pi numbers than 10 cores.

How is this possible? Is there somekind of logical explanation?

Thanks in advance!

 

[spirit]

maybe it could be memory access, because 10cores is more than 8 on 1socket.

pvetest repository have a new vm config option (numa:1) to improve that. (need kernel 3.10 too)

 

[cm350]

Hi,

The Prime test looks good with 8-cores. I think we are going to change it over night to the exchange servers. I'll give you some feedback!

Thank you very much!

 

[udo]

Hi,

The Prime test looks good with 8-cores. I think we are going to change it over night to the exchange servers. I'll give you some feedback!

Thank you very much!

Hi,
only for curiosity, do you have HT enabled, or not?

Because with HT 10vcores can be on one CPU.

Udo