Re: small i & power systems (disk performance)

ChadB@xxxxxxxxxxxxxxxxxxxx wrote:

The new DASD and cache oriented controllers are very good performers. The
integrated 5727 controller has done very well for us on both DB2 based
systems and WAS/Domino setups. If at all possible, see if your business
partner can get some modeling done for you by Randy Watson's company
Midrange Performance Group (you can collect a period of current performance
data, easily send it to them, and they can send you 'What If' modeling back
against various blends of controller/disk setups. If your BP doesn't work
with MPG as a service, I think MPG also will sell you this service at a
pretty reasonable price (getting the right hardware spec'd with some expert
assurance based on hard data can be pretty valuable). The only thing i've
heard to really watch out for still is 3 drive RAID setups... that may have
been fixed in the last year or two, though.

BP had us load MPG's Performance Navigator on PC. Makes it easier to download the collected data for the BP.

The 3 drive RAID5 set issue is not unique to i. RAID5's weakness is on data writes where the parity needs to be calculated and written as well. With 3 drives, 1/3 of the write operations are parity. With larger sets this parity write overhead goes down. A large cache controller helps, but it's probably cheaper to just add more disk.


Keith