RE: Mirroring redo log groups or not ?
- From: "Timur Akhmadeev" <Akhmadeev@xxxxxxxxxxxxxx>
- To: <Jon.Crisler@xxxxxxx>,<oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 8 Apr 2009 11:56:34 +0400
Good point to start: Tuning 'log file sync' wait events
<http://orainternals.wordpress.com/2008/07/07/tuning-log-file-sync-wait-
events/>
Thanks,
Timur Akhmadeev
________________________________
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Crisler, Jon
Sent: Tuesday, April 07, 2009 8:17 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: Mirroring redo log groups or not ?
I am dealing with a possible performance issue with "redo log sync
wait". This is for 10g 10.2.0.4 on Linux 64. In troubleshooting
this problem, one of the things I did was to cut down the redo logs so
that there is only 1 member per group rather than 2 (i.e. redo log
mirroring). Each member goes to a different LUN, and the LUN's are
Raid-5.
Here is the layout-
LUN 1 is 1 TB approx, Raid-5 used for database files
LUN 2 is 500 gb Raid 5 used for RMAN backups to disk,
LUN 3 is 500 gb Raid 5 used for archive log destination
All are SAN connected via 2 - 4gb Qlogic HBA's with multipath.
Now, currently online redo logs are going to Lun 2 for the first member
and Lun 3 for the second. So there is going to be a little bit of
contention when archiving, but whichever LUN I point to is going to
encountered contention. It would be very difficult to add more LUN's
due to SAN restrictions, but I have the option of converting either LUN
2 or 3 to Raid 1 / 0. If I converted to Raid 1/0 I could point one or
both members to this LUN. There appears to be some performance
difference with our hardware between Raid 1 and Raid 5, but not a great
deal in actual testing.
So, if the LUN that holds the online redo logs is already protected
(raid 1, 5 etc) do I really need to mirror the online redo logs ?
Should I convert the LUN to Raid 1 / 0 ? if I convert to Raid 1/ 0
should I keep redo log mirroring and point to the same LUN ?
The information transmitted herein is intended only for the person or entity to
which it is addressed and may contain confidential, proprietary and/or
privileged material. Any review, retransmission, dissemination or other use of,
or taking of any action in reliance upon, this information by persons or
entities other than the intended recipient is prohibited. If you received this
in error, please contact the sender and delete the material from any computer.
Other related posts:
