> -----Original Message----- > From: Nguyen, Bao L [mailto:[EMAIL PROTECTED]] > Sent: Freitag, 10. Januar 2003 22:45 > To: [EMAIL PROTECTED] > Subject: LiveCache 7.4 - Should I use Dual Log Mode or Not? > > > Hi All, > > According to the "Checklist for recovery of SAP APO liveCache > 7.4" by Werner Thesing, it is recommended to mirror the > LiveCache log in production. However, I concern about the > impact on Livecache performance if we use the dual log mode > for our Livecache 7.4. How much the dual log mode can impact > to Livecache performance in contrast to the single log mode? > > Thanks. > > Bao Nguyen > > Bao L. Nguyen > SAP APS SE Team > Ph: 916-356-0705 > Pgr: 916-857-2755 > Hi, this is not a liveCache specific issue, but for all SAPDB instances.
If you use a separate controller and disks for the mirrored log devices, you will not loose performance notable, since writing activity on both disk is done asynchrously in separated threads for each device. Only if the mirrored log devices writing collides with other disk activity, you will loose performance. During reading from log (restart) you will even gain performance, since the reading is done like in a RAID 1 hardware (reading from both disks can be done in parallel...). Another good reason to keep the log devices separated from other disk activity, is that log information is written in streaming mode on the disk, which is only fast, if no other seek activity happens on that disk in parallel... So independent from your disk choice, for best software performance and security use separated log devices - which are really for log only - on separated controllers in a dual log configuration. CU jrg _______________________________________________ sapdb.general mailing list [EMAIL PROTECTED] http://listserv.sap.com/mailman/listinfo/sapdb.general
