Re: Multiplex Redo Logs with Mirrored Disks?

  • From: "Richard Foote" <richard.foote@xxxxxxxxxxx>
  • To: <dwagoner@xxxxxxxxxxxxxxxxxx>, "ORACLE-L (E-mail)" <oracle-l@xxxxxxxxxxxxx>
  • Date: Wed, 24 Nov 2004 07:43:48 +1000

Hi David


There are 3 things you need to fully recover an Oracle database. A complete 
backup, all the redo logs since the backup and a DBA who know what there're 
doing. Relying on hardware mirroring to protect your "precious" redo logs is 
a risky business as it does not protect you from many possible failure 
scenarios (disk controller failure/corruption, single LGWR write corruption, 
accidental deletion, etc.).  Therefore, it can potentially compromise the 
2nd criteria and put into question the 3rd.

Any database review that does not include multiple redo log members gets a 
(not so little) cross IMHO.


----- Original Message ----- 
From: "David Wagoner" <dwagoner@xxxxxxxxxxxxxxxxxx>
To: "ORACLE-L (E-mail)" <oracle-l@xxxxxxxxxxxxx>
Sent: Wednesday, November 24, 2004 1:46 AM
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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