Andrej Falout schrieb: > > In article <B9A2DDA03044D311BBD40008C75D69680B3719E4@dewdfx24>, > [EMAIL PROTECTED] says... > > Hi, > > since SAPDB does not use any feature of a filesystem for its volumes(alias >devspaces) > > any kind of filesystem overhead including a buffer cache is just an overhead. >SAPDB opens > > using O_SYNC, but O_DIRECT is not yet used. All Read/Write activity use Systempages > > which are aligned to 4KByte. The LINUX > > raw devices which are preferred are those 'unbuffered' /dev/raw/rawX. > > CU > > jrg > > just tried using /dev/mdx (Linux SW RAID device) using RAID5, seems to be > working. What should I expect in the therms of performance, compared with > cooked FS? Any optimisation/configuration tips for RAID- strip sizes and > similar? > > (Yes I know hardware RAID is supposed to be faster, but this is no longer true > - in most cases. Try >1 CPU over 2MHz plus LVD 160 controller, if you have more > then 4 disks, spread over 2 SCSI busses. Now measure, and compare with HW > controllers. Just don't compare it with controllers costing more and with more > RAM then the whole server box, please - "let's be reasonable" (TM & famous last > words).)
True. I've using Software RAID on Linux for years. It's great. I even removed HW SCSI RAID controller because SW RAID gave better performance. If you want the most performance out of your disks, create RAID10. The order is very important here: create two RAID1 devices, then create one RAID0 with them. Don't do it the other way around. Simon > > Hmmmm, just tried taking one disk down - all fine, CPU at 34% when doing full > table select joining on fields without index... > > Reinserted disk, same select on top of disk rebuilding had CPU at 13%. Rebuild > of 9GM partition completed in 22 minutes, with database constantly doing full > table selects with hash joins... > > Looks good! > > -- > Yours, Andrej Falout, http://www.falout.com/disclaimer.html > Visit the OpenSource alternative, Aubit 4gl: http://aubit4gl.sourceforge.net > PLEASE NOTE: All HTML email sent to me WILL BE DELETED AUTOMATICALLY WITHOUT > READING. > > _______________________________________________ > 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
