Can you be more specific about your disk setup? How fast is "fast scsi"? 15K + U160? How many disks are in your RAID 5 array? How big is the onboard cache (if any)? And how large are the (100?) records you're updating?
If the differences are really big, I would wonder about that stuff more than the db (does it happen with other rdbms?)... On Fri, 2002-10-18 at 21:36, Robert Kr�ger wrote: > > Hi, > > we have a write performance problem that I hope maybe someone could shed some > light on. > > we have two linux servers, roughly equivalent regarding CPUs and memory > running the same OS version (Kernal 2.4 SuSe 8.1) and the same version of > sapdb with almost identical configuration (as far as I can tell relevant for > write performance). We noticed a big difference in write performance (we have > a little java tool that issues many inserts and commits each 100 records), > i.e. one system is 5 times faster than the others, while read performance is > nearly identical. The main diffference is that the fast system uses a RAID5 > system while the slow system uses a fast scsi disc. since this is an obvious > thing to look for we performed filesystem benchmarks using the IOzone > benchmark tool (http://www.iozone.org) and found a big difference in the > write (in IOzone terms, writing to a newly created file) performance for > small block sizes, that would explain the difference in database write > performance as the order of magnitude of the difference is roughly that of > the difference in insert-performance. > > However, the rewrite performance (in IOzone terms, writing to an already > existing file) is even better for the "slow" system. I thought sapdb writes > to existing files and therefore that number is the relevant one destroying my > theory that disc write performance is the problem. > > Another strange thing is that on the "slow" machine stopping the database also > takes ages compared to the "fast" system. > > Can anyone explain that or take a guess? > > Thanks, > > Robert > > > > > _______________________________________________ > sapdb.general mailing list > [EMAIL PROTECTED] > http://listserv.sap.com/mailman/listinfo/sapdb.general _______________________________________________ sapdb.general mailing list [EMAIL PROTECTED] http://listserv.sap.com/mailman/listinfo/sapdb.general
