Re: new RS/6000: from 8*250MHz to 2*750MHz - what to expect

Erik Ykema wrote:
> Esteemed Oracle practicioners,
> I would appreciate your thoughts on our RS/6000-change.
> Our operations manager has decided that our current RS/6000 (8 cpus at 250
> MHz) machine should be replaced by a new one having just two 750 MHz
> processors. The cause is Oracle's license structure: per CPU.
> On this machine we have one instance for our datawarehouse (Oracle 8.0.6 -
> we have not planned to upgrade yet, AIX4): nightly batches in Pro*C and
> SQL*Plus-scripts; during daytime it works for our OLTP users in maximum of 7
> concurrent running reports.
> Lot of batch SQL has been tuned by trial and error (choosing the degree on
> the tables; parallel hints) in order to have the batches fit in the tight
> night processing window. Of course we will have to test everything in
> pre-production phase. Additional tuning will end on my plate... and I try to
> achieve some kind of work load planning for the coming half.
> From sar I have learned that, as usual, the disks are the main unix
> wait-events and that hardly ever, in batch or in OLTP, 100% CPU utilization
> is reached. During batch this is also due to wait-constraints in the batch
> job chain.
> What should I be aware of regarding performance? And any other pleasant or
> unpleasant suprises? (I have roamed the c.d.o.* newsgroups but could not
> find much insight.)
> Thanks,
> Erik Ykema
> Oracle Analyst/Programmer
>

Cpu is not everything. Sometimes upgrading or adding cpu(s) make things worse!
That's the case, when the system is io-bound, and batch jobs running at full cpu speed (as parallel query, reports.....) issue more io-requests in a given time frame. Then everybody battling for io-bandwith suffers.

If your current system is cpu-bound (near 100%), then the new 2 cpu system will be less productive. Performance goes down.

If Your current system is io-bound (near disk saturation, sar or other loved tool may tell) and your cpu's are several marks from 100% usage, then you may gain on elapsed time. Better performance.

Both are only true in the case the new system has similar or same disk sub system.

Else you have to grap the calculator to do a qualified guess or do a real time test to make sure.

rgds

/Svend Jensen Received on Fri Mar 14 2003 - 13:23:23 CST