On Fri, 2006-04-07 at 12:58, Gavin Hamill wrote:
> Bing-bong, passenger announcement.. the panic train is now pulling into
> platform 8.1.3. Bing-bong. =)
>
> OK, having moved from our quad-xeon to an 8-CPU IBM pSeries 650
> (8x1.45GHz POWER4 instead of 4 x 3GHz Xeon), our query times have shot
> up and our website is next to unusable. The IBM is not swapping (not
> with 16GB of RAM!), disk i/o is low, but there must be something
> critically wrong for this monster to be performing so badly..
>
> There is little IO (maybe 500KB/sec), but the CPUs are often at 100%
> usage.
Can you test your AIX box with linux on it? It may well be that
something in AIX is causing this performance problem. I know that on
the same SPARC hardware, a postgresql database is 2 or more times faster
on top of linux or BSD than it is on solaris, at least it was back a few
years ago when I tested it.
Are the same queries getting the same basic execution plan on both
boxes? Turn on logging for slow queries, and explain analyze them on
both machines to see if they are.
If they aren't, figure out why.
I'd put the old 4 way Xeon back in production and do some serious
testing of this pSeries machine. IBM should be willing to help you, I
hope.
My guess is that this is an OS issue. Maybe there are AIX tweaks that
will get it up to the same or higher level of performance as your four
way xeon. Maybe there aren't.
Myself, I'd throw a spare drive in for the OS, put some flavor of linux
on it
http://www-1.ibm.com/partnerworld/pwhome.nsf/weblook/pat_linux_learn_why_power.html
and do some load testing there. If the machine can't perform up to
snuff with the same basic OS and a similar setup to your Xeon, send it
back to IBM and buy one of these:
http://www.asaservers.com/system_dept.asp?dept_id=SD-002
or something similar. I can't imagine it costing more than a pSeries.
