Oracle FAQ Your Portal to the Oracle Knowledge Grid

Home -> Community -> Mailing Lists -> Oracle-L -> Re: Redo Logs - Raid 1 or No Raid

Re: Redo Logs - Raid 1 or No Raid

From: Tanel Poder <>
Date: Fri, 15 Aug 2003 08:14:35 -0800
Message-ID: <>

Redo Logs - Raid 1 or No RaidHi!

If your system isnt very transaction active and you want simplicity, then just go with one set or RAID-1 (2 disks) and put all your groups onto this set. (no multiplexing). And use other 2 disks elsewhere.

But if you have high transaction activity (hence great redo write activity) *and* you are in archivelog mode, then yes, put your even numbered groups to one RAID1 set and odd-numbered ones to another set. That way ARCH process won't contend with LGWR when readin filled logs for archiving.

And if you want high recoverability (not talking about reliability on Windows), you might even want to use your 4 disks not RAIDed at all. Just multiplex your redologs with Oracle means, possibly separating members of redologs across controllers. That way you could even survive controller, OS, filesystem glitches, but you have to manually recreate missing logfiles after a media failure. But Oracle will continue working as long as it can write to at least one member of redolog group. Also it increases CPU usage a little bit (2 redo writes have to be done instead of 1). One thing to check is how Windows behaves when it suddenly looses a disk/filesystem. Maybe it'll stop behaving at all under these circumstances.


  Hello all

  Oracle 8.1.7
  Windoze 2000
  Archive Mode - OLTP System

  Which do you think is a better set up for the Redo Logs:    2 Groups on 2 Raid1 or 4 Groups on 4 separate non-raid disks?   Granted you gain fault tolerance with the mirriored pair, but is that really needed if you multiplex group members over 4 different disks?

  As usual we are working with clients that have limited number of disks to work, so 4 Raid1's is not an option ;)

  Does anyone have multiple log groups on the same physical drive(s). For example, 4 log groups, 2 members each, with group

  1&3 on drive A, and 2&4 on drive B? Does this really gain you anything?

  Any ideas and comments are welcome. Thanks for all the help.

  David Phillips
  Support DBA


Please see the official ORACLE-L FAQ:

Author: Tanel Poder

Fat City Network Services    -- 858-538-5051
San Diego, California        -- Mailing list and web hosting services
To REMOVE yourself from this mailing list, send an E-Mail message to: (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). Received on Fri Aug 15 2003 - 11:14:35 CDT

Original text of this message