RE: Oracle RAC cost justification?

I need some help with the argument about the VAX and Alpha architectures here, Mladen! I've been away from it too long...

Rich

-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Tim Gorman Sent: Thursday, June 02, 2005 11:56 PM
To: oracle-l_at_freelists.org
Subject: Re: Oracle RAC cost justification?

SMP (a.k.a. "symmetric multiprocessing") actually exists in only one platform -- IBM. That's why it only scales to 32 CPUs, because the problem
is connections. You can only connect so many CPUs to the same memory. But
they are all "equi-distant" from any address in memory.

Other platforms are actually closer to what used to be called NUMA (a.k.a.
"non-uniform memory access"), because CPUs and RAM are clustered
together on
boards that communicate over a bus, thus causing some memory to be
"closer"

to some CPUs than other. If a CPU wants info from memory address XXX, then
perhaps that is available on the same board, no need to go over the bus. However, if that same CPU wants info from memory address YYY, then perhaps
that is on another board, so we have to go across the bus to the other board. Sun and HP architectures fall into this category, even though both
are commonly referred to as "SMP" as well.

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