Re: Wildfire/Oracle/NUMA/QBB affinity on OpenVms/Oracle73

On Mon, 5 Feb 2001 22:13:27 -0000, "Snops" <simon.maufe_at_virgin.net> wrote:

>Hello, this is really an oracle oracle question, not Rdb. I've cross-posted
>to Rdb since I know many participants use Oracle Oracle. My issue is we
>installed a new bigger server, and performance went down! Once we turned off
>4 CPUs and the users were only on the remaining, the application speeed up!
>We've since discovered there is a 3 times performance penalty when
>a user's process is on 1 QBB, and the SGA is on another. Then the memory
>request goes across a bridge or L2 cache, and there seems to be serious
>problems here.
>

Interesting. Not surprised at all. I've often had nasty surprises in performance with NUMA-Q hardware. As soon as there is X-quad comms, the performance goes down the drain. Goes for Sequents too. Kills the I/O throughput on those too.

In one of the latest ORACLE books (Scaling ORACLE 8i, James Morle), there is a very interesting explanation of one of the possible reasons why. That architecture is not really suited (in its current form!) to software that uses large amounts of shared memory with lots of processes/tasks accessing said memory. Which just about means any modern database.

With new releases for that specific h/w, it's possible the problem will go away, although I doubt it will be a complete solution.

In the meantime, you could try to start the database engine in a single quad. With Sequents, I believe there is a way to do this. With Compaqs, sorry but I don't know. That would be better than taking a 3X hit.

Another possibility mentioned a while ago here was to have Parallel Server, with each quad behaving as a database node. I don't know if anyone has done work in this direction, but for some types of applications it would make sense.

Cheers
Nuno Souto
nsouto_at_bigpond.net.au.nospam
http://www.users.bigpond.net.au/the_Den/index.html Received on Tue Feb 06 2001 - 03:04:03 CST