I'm contemplating building a new NAS using a dual socket MB. I know that RAM slots & PCI-E slots are divided up/managed between the two sockets. IE: RAM in the 2nd bank won't recognize without a CPU in the second socket.

 

Does the mix management of RAM & PCI-E slots affect VM's or do the VM's have to be split along socket lines too?

 

Basically, can a VM be assigned RAM that is being managed by both sockets (like most available RAM)? If a VM is bound to socket 0, can it use a PCI device managed by socket 1? That kinda thing.

AFAIK, VM's are unaware of RAM being divide between sockets as are PCI devices, it's not an issue. To a VM RAM is RAM, a PCI device is just that.

I've assigned one of my vm's 42gb of ram out of the 72gb I have on a dual processor proliant. The vm didn't seem to care. I've never paid attention to what cards are on what lanes that get passed through and haven't had any issues from that either.

Interesting. I'll need to do some searching to see if anyone has done performance testing on same socket RAM/devices vs cross socket.

Would be very interested to know if you got anywhere with testing the allocation of pci-e lanes/threads of an "indirectly connected" socket to a VM? How did you identify which threads were paired with which lane, and were there any issues caused with crossing the two over?

I could have sworn that I've read something more detailed about this in the forums but after an hour or so of scouring the web I can't seem to stumble across it again. Any pointers would be greatly appreciated!