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RE: Multiplex Redo Logs with Mirrored Disks?

From: Hand, Michael T <>
Date: Tue, 23 Nov 2004 15:05:49 -0500
Message-ID: <>

The 2 reasons for keeping redundant Oracle mirroring in a disk HW/SW mirrored environment are:

  1. The operator error factor. Much lower risk of accidental deletion when there are 2 file per group than one, and
  2. Physical corruption - now I know this is not supposed to happen with all this RAID and SAN stuff, but I've crossed that bridge and came out only lightly toasted.

If you can live with those two risk factors, as Dick has said, disk based mirrors are more efficient.

Mike Hand

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

From: Goulet, Dick [] Sent: Tuesday, November 23, 2004 11:50 AM To: ORACLE-L (E-mail)
Subject: RE: Multiplex Redo Logs with Mirrored Disks?

On a mirrored disk system, I don't multiples the redo logs. First off the disk subsystem is much more efficient at the job than Oracle. Second it becomes redundant storage.=20

Dick Goulet
Senior Oracle DBA
Oracle Certified 8i DBA
-----Original Message-----

From: David Wagoner []=20 Sent: Tuesday, November 23, 2004 10:47 AM 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



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-- Received on Tue Nov 23 2004 - 16:57:04 CST

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