Re: disk cache useful?

Scott Winger (swinger_at_mailsrvr.bussvc.wisc.edu) wrote:
: We currently have an IBM RS/6000 C20 (Power PC 604, 64 Mb RAM, 2.2Gb disk)
: which is running AIX V4.1.4 and Oracle 7.1.6.
 

: We are debating whether an L2 cache would be worth purchasing for this machine.
 SNIP...
: My guess is that if we want to improve response time, more RAM and/or a
: RAID disk system would be a better place to invest than in an L2 cache.

Adding more RAM would help, as far as disk caching, if you add a LOT of RAM. OTOH, more RAM could mean that you could increase the size of your SGA, which might be (probably) a good thing.

As to RAID, this would probably give you the best improvement in throughput. If you don't need the reliability of RAID5 (and since you don't already have it, you probably dont), then don't use it. Use RAID1 instead. I hope I have the right RAID number here, as I seem to have taken my reference home. In any case, RAID5 provides striping with parity. Read performance is very good, but write performance takes a hit. If you don't need the added reliability of RAID5, RAID1 provides striping, only. Think of RAID1 as a large, VERY fast, disk.

Later.

--
Bob Stewart                     ASE
(310) 335-7152                  Air Transportation Division
bob_at_latcost1.alaao.ats.eds.com

I am definitely NOT speaking for EDS.