Oracle-L: Re: duplexing redos and archives

From: <Jared.Still_at_radisys.com>
Date: Tue, 06 Aug 2002 12:29:06 -0800
Message-ID: <F001.004AC982.20020806122906@fatcity.com>

RAID 0 is not mirroring, but simply a stripe of several individual disks.

RAID 5? In the immortal words of King Arthur in "Monty Python and the Holy Grail", "Run away!"

If your database is a transactional system, RAID5 is not for you.

It's very slow for writes. A google search should turn up more than you want to know. :)

As for your SA's contention that mirroring your redo logs is no longer necessary, don't believe it. Your redo logs and archived redo logs are the most important physical parts of your database in a recovery scenario.

And if they're soft mirrored via Oracle, your database will continue to work when someone indavertantly removes one of your log files.

Jared

Joe Armstrong-Champ <Joseph.Armstrong-Champ_at_tufts.edu> Sent by: root_at_fatcity.com
08/06/2002 11:13 AM
Please respond to ORACLE-L

        To:     Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
        cc: 
        Subject:        duplexing redos and archives

Currently we are duplexing our redo logs and archive logs through oracle. We do this at the oracle level because we are using mirroring (raid0?) and if we lose a redo log or archive file the database will not be affected.

We will be moving to raid5 arrays in the future and are wondering whether we still need to do the duplexing. Since the arrays are made up of data disks plus a parity disk plus a hot swap do we need to worry about losing a redo log? Our sys admins are telling us we don't and I tend to agree with them but we want to get other opinions on the subject.

How are shops handling this who are using raid5?

Thanks.
Joe
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Author: Joe Armstrong-Champ
INET: Joseph.Armstrong-Champ_at_tufts.edu

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