upgrading RAM in a server [dell poweredge T610]

Question

While this may come off as yet another ram question it is slightly different in what I have seen covered.

I've updated my own ram before, but this is throwing me off for two reasons. One, it is a server that has two processors. Which is nice, but does each processor need to have matching ram? what are the rules when dealing with two processors

The seoncond questions is what to make of what I have

All I know about them is what the invoice says '224GB Memory (6x4GB), 1333MHz Dual Ranked LV RDIMMs for 1 Proc, Optimized ' (note this machine was not purchased by me. It was purchased early last winter)

I have six open slots and would like too add 6x8gb and triple the memory available. But I am having a hard time figuring out what I have from the above line. So would something like this work http://www.newegg.com/Product/Product.aspx?Item=N82E16820139273 (x2): Kingston 24GB (3 x 8GB) 240-Pin DDR3 SDRAM ECC Registered DDR3 1333 (PC3 10600) Server Memory Model KVR1333D3D4R9SK3/24G

I'm using linux/centOs5.5 if that matters to anyone.

Answer 1

There are significant benefits to keeping the same amount of RAM on each channel of a single CPU. There are some benefits, but not much, to keeping the same amount of RAM on each CPU.

Each CPU can access memory connected to the other CPU almost as efficiently as it can access its own. It's so close to the same that today's operating systems and software don't even bother to track it -- they don't try to run tasks on CPU 'close' to the memory they need or allocate memory 'close' to the CPU that's going to use it.

However, by evening out the memory, you do prevent memory controller channels from being a bottleneck. If you have two CPUs each with two channels, putting the same amount of memory on each of the four channels helps to even out the load -- a channel with more RAM than the others wouldn't tend to become a bottleneck. It also permits the CPU to interleave across its channels. Interleaving across CPUs is not done.