Oracle FAQ Your Portal to the Oracle Knowledge Grid

Home -> Community -> Mailing Lists -> Oracle-L -> RE: Multiplex Redo Logs with Mirrored Disks?

RE: Multiplex Redo Logs with Mirrored Disks?

From: Stephen Evans <>
Date: Tue, 23 Nov 2004 15:11:33 -0500
Message-ID: <>

i have experienced multi disk failures within a single raid group. it always seems to happen after the array has been powered off (i guess the spindles seize or something).
so, yes multiplex your redos & cf's

we actually tri-plex redos & controlfiles. one copy goes on local unix storage & the other two go on the SAN. That way even if the SAN catches on fire (or whatever), we can still get to our active redos & control files.

good luck,


"Nick Tilbury @ Northampton" <ntilbury
Sent by:
11/23/2004 11:48 AM
Please respond to ntilbury  

        To: "''" <>, "ORACLE-L (E-mail)" <>

        Subject:        RE: Multiplex Redo Logs with Mirrored Disks?

IMHO - What you are questionning is 'best-practice' and relying on hardware
solutions to get
you out of any potential failures. I'd say your on a slippery slope. Stick with best practice and have at least 2 members per group.

-----Original Message-----

[]On Behalf Of David Wagoner Sent: 23 November 2004 15:47
To: ORACLE-L (E-mail)
Subject: Multiplex Redo Logs with Mirrored Disks?

Is there any need to multiplex redo logs with mirrored disks (e.g., RAID-1 or RAID-1+0)?
Example- Oracle recommends multiplexing redo logs on separate disks, like redo01a.log on Disk1 and redo01b.log on Disk2, etc.

However, now that mirrored disks are in common use with RAID-1+0, RAID-1, etc. it seems that sufficient protection is in place to use only a single copy of each redo log. This would also provide the benefit of reduced disk
I/O to write redo information to disk.

Anyone disagree?

Best regards,

David B. Wagoner
Database Administrator


This message is intended solely for the use of the individual or organisation to whom it is addressed. It may contain privileged or confidential information. If you have received this message in error, please notify the originator immediately. If you are not the intended recipient, you should not use, copy, alter, or disclose the contents of this message. All information or opinions expressed in this message and/or any attachments are those of the author and are not necessarily those of VarTecTelecom Europe Ltd or its affiliates. VarTec Telecom Europe Ltd accepts no responsibility for loss or damage arising from its use, including damage from virus.


-- Received on Tue Nov 23 2004 - 17:04:12 CST

Original text of this message