Don, I guess that it is a known issue of compression performance with RMAN in 10.1 and 10.2. That is probably why Oracle 11g has a new compression algorithm, with which the performance of RMAN compression is noticeably faster than in previous releases. I did a benchmark testing last year in both 10.1 and 10.2 databases in a Solaris box with 16 processors. When compression is enabled (no parallelism), RMAN backup takes about 5 times longer than the one without compression, and the backupsets size is about 5 times smaller. That was the reason I thought the compression option in RMAN in 10.1 and 10.2 is not practical, especially for restore and recovery. Hope this helps, Limin. On Nov 16, 2007 1:27 AM, Don Seiler <don@xxxxxxxxx> wrote: > Some quick answers to these questions before I hop into bed. > > > 1. What version is this..? Are you using a block > > tracking file for your incrementals? If not you may be > > backing up way more information than you need too. > > Sorry for not mentioning this straight away. This is Oracle EE > 10.2.0.2 on RHEL4. Processing is 4 dual-core 64-bit CPUs. Both RDBMS > and OS are 64-bit. > > Yes we use BCT for incrementals. Our level 1 incrementals take > anywhere from 30 to 90 minutes. Our schedule is to do a level 0 on > Saturday evening, and level 1 on all other evenings during the week. > > > 2. Are you doing your parallel backups to the same > > disk? You could be running into disk contention if so. > > Yes we are (to /rman), and this is my first hunch. Shamefully, I'm > not well-versed by any means with the storage side of database > operations. If this Veritas partition were striped across multiple > disks, does that mean anything in terms of being able to support > parallel writes? Or should I only think of it as 1 and not try to > play games? > > > 3. What is your CPU usage during the backup. As > > mentioned earlier, if you are CPU constrained then > > compression can slow things down. If you are not CPU > > constrained then compression can very much speed > > things up and make your backup images much smaller. > > The load sometimes goes over 21.00. If you're looking for a different > metric I can try to get that as well. > > Obviously storage space was the reason we use compression here, and > especially the reason we don't do the incremental merge scenario that > Job mentioned. Incremental merge does an image copy of all data files > for the base image. A normal uncompressed backup would at least skip > whatever empty and/or unused blocks, if I recall correctly. > > I'd like to get a picture of the ideal backup-to-disk scenario with a > goal of minimizing backup and especially restore/recovery. Should I > have 4 partitions on physically separate spindles for the 4 parallel > jobs? Suck it up and do the incremental merge (although I don't see > that affecting restore/recovery time)? Just not do compression? With > a recovery window of 7 days it might take up quite a bit more disk (is > "disk is cheap" still the fashionable response?). > > > -- > Don Seiler > http://seilerwerks.wordpress.com > ultimate: http://www.mufc.us > -- > //www.freelists.org/webpage/oracle-l > > > -- Regards, Limin Guo. -- //www.freelists.org/webpage/oracle-l