What's a NUMA?

While working with SAP and ORACLE on HPUX systems in recent years I've had to configure many a "NUMA" related parameter - well who hasn't these days?

So that I don't have to pretend to my wife that I know what that is I think I should probably find out and blog it here (as actually she doesn't care... of course)

I attended a good webconf today on tuning memory in HPUX systems. They mentioned NUMA architecture and tuning shared memory vs CLM - or Cell-Local-Memory, which is essentially memory local to the processor (in a multi-processor server, or servers).

And that's where NUMA is the paradigm - it stands for Non-Uniform Memory Access (NUMA) and covers the design of systems with both memory that is locally assigned to processors and shared or interleaved memory that is shared between processors.

I won't go into much detail on L2, L3 and L4 caches as I cannot talk with great authority and I'm sure Google can well you... for a start though if it interests you checkout the NUMA entry in Wikipedia.... http://en.wikipedia.org/wiki/Non-Uniform_Memory_Access