there's a faster (but less efficient) compression option in 11g so that tape drives keep streaming. Part of the Advanced Compression option ($$) ... http://www.oracle.com/technology/products/database/compression/faq.html#I_am_already_using_the_RMAN_backup 2009/4/23 Howard Latham <howard.latham@xxxxxxxxx> > I had to give up compression as it slows restores so much. At UKOUG last > year we discussed RMAN best practice - I think it was something Oracle was > working on. > > 2009/4/23 Kenneth Naim <kennaim@xxxxxxxxx> > >> As in all situations it depends; it depends on how many channels are >> being used, how fast the cpu’s are, what media the backup is going too, how >> many tape/disk drive are being read from and to, the speed and type of the >> network between all the points, and the amount of work happening while the >> backup is running. As a broad generalization slow cpu’s with one or few >> channels and a fast IO subsystem will result in a slower backup when >> compression is added or in other words if CPU is the bottleneck in your >> backup, compression is not recommended. >> >> >> >> I did an analysis of my clients backup system, where political fingers >> were being pointed in every direction and each piece of the system was >> believed to be at fault by a different group. A 6+tb 10gr2 database was >> being backed up from 150 drive raid 0+1 SAN to a 3 drive tape library system >> using 24 channels connected via gigabit Ethernet on 12 cpu/24 core Sun 2900. >> By reviewing the data in the V$BACKUP_SYNC_IO and V$BACKUP_ASYNC_IO views I >> proved that the bottleneck was on the gigabit network, and that the san was >> barely being touched. Due to the politics several components were changed >> simultaneously, the Ethernet to tape was replaced with a single channel 2gb >> fiber to 160 disk ibm xiv array disk and compression was added. Performance >> went from 18 hours to under 5. The single fiber card is our new bottleneck >> and performance should improve once our os team, sun and ibm figure out why >> the second card is not playing nice. >> >> >> >> Ken >> >> >> >> *From:* oracle-l-bounce@xxxxxxxxxxxxx [mailto: >> oracle-l-bounce@xxxxxxxxxxxxx] *On Behalf Of *Tony van Lingen >> *Sent:* Wednesday, April 22, 2009 9:16 PM >> *To:* robertgfreeman@xxxxxxxxx; oracle-l@xxxxxxxxxxxxx >> *Subject:* Re: compressed backup - is this a reasonable size >> >> >> >> That is interesting. I was just discussing this with my collegue who >> specialises in RMAN backups. He asserts exactly the opposite where it comes >> to backup times. As an example, we have an GIS database of about 1TB (10g) >> which backs up in 30 mins in standard mode. When he enables compression it >> takes up to 6 hours and is very cpu intensive. Apart from that, he agrees >> that the compression is quite good. >> >> Apparently the compression also should not be used in combination with a >> compressed tape device. >> >> Cheers, >> Tony >> >> Robert Freeman wrote: >> >> Very reasonable. Compression can do wonders for the size of backup sets! >> It can also significantly improve overall backup times. What were your times >> for the backup compressed and non-compressed and how much of a difference in >> CPU did they make. >> >> Be aware that someone on here mentioned a bug with compression just a few >> days ago.I looked in Metalink for compression related bugs and found a few. >> In a very quick looksee I find most the bugs seem to be related to backups >> as opposed to restores. So it seems if you can get a good backup, then you >> might well be ok. As always, test test test, your restores. No piece of >> software is perfect! :-) On a regular basis continue to test your restores >> just in case a bug creeps in. My personal experience with Compression has >> been very positive. >> >> Robert >> >> >> >> Robert G. Freeman >> Author: >> OCP: Oracle Database 11g Administrator Certified Professional Study Guide >> (Sybex) >> Oracle Database 11g New Features (Oracle Press) >> Portable DBA: Oracle (Oracle Press) >> Oracle Database 10g New Features (Oracle Press) >> Oracle9i RMAN Backup and Recovery (Oracle Press) >> Oracle9i New Features (Oracle Press) >> Other various titles out of print now... >> Blog: http://robertgfreeman.blogspot.com >> The LDS Church is looking for DBA's. You do have to be a Church member in >> good standing. A lot of kind people write me, concerned I may be breaking >> the law by saying you have to be a Church member. It's legal I promise! >> :-) >> >> >> >> >> ------------------------------ >> >> *From:* Jeffrey Beckstrom <JBECKSTROM@xxxxxxxxx> <JBECKSTROM@xxxxxxxxx> >> *To:* oracle-l-freelists <oracle-l@xxxxxxxxxxxxx><oracle-l@xxxxxxxxxxxxx>; >> oracle-db-l >> <oracle-db-l@xxxxxxxxxxxxxxxxxxxx><oracle-db-l@xxxxxxxxxxxxxxxxxxxx> >> *Sent:* Wednesday, April 22, 2009 7:36:52 AM >> *Subject:* compressed backup - is this a reasonable size >> >> Just ran the following command. This is our first RMAN backup. It backed >> up a 17G database into about 3G of files. Is this reasonable????? >> >> >> >> backup as compressed backupset database plus archivelog delete input; >> >> >> >> Backup states it finished normally. >> >> >> >> Jeffrey Beckstrom >> Database Administrator >> Greater Cleveland Regional Transit Authority >> 1240 W. 6th Street >> Cleveland, Ohio 44113 >> > > > > -- > Howard A. Latham > > >