Re: redo log duplexing question

Unix mirroring should be transparent to the application. The redo logs, and all other files for that matter, are referenced in Oracle by their mount points, ie. /oradata/logs/redo01.log etc. In a nutshell, Unix mirroring simply allocates multiple locations to service the same mount point, so the loss of the disk that the primary copy of the file resides on should not cause a problem for Oracle, as the secondary copy contains an exact copy of what was on the primary disk, mount-point reference and all.

So, to answer your question, I think it is a matter of preference whether you use disk mirroring or redo log multiplexing. I have setup systems both ways, and have not really seen a benefit of one over the other, although I haven't really done any benchmarking or other testing.  You don't need to do both, and yes you may see a performance degradation if you do.

HTH,
Roy

In article <380e0680.22405810_at_news.demon.nl>,   postbus_at_sybrandb.demon.nl (Sybrand Bakker) wrote:
> On 20 Oct 1999 13:51:21 -0400, buzzwang_at_churchill.ourvillage.com
> (David F. Newman) wrote:
>
> >Hi,
> > I was once told in the backup and recovery
> >class that it is a good idea to
> >
> >1) Mirror the disk that redo logs sit on and
> >2) Duplex the redo logs themselves.
> >
> >So, essentially, each redo group exists on
> >four disks. I've been doing that but it has
> >come up that it might be a performance issue
> >writting to four locations for each redo group.
> >I honestly can't remember the reason for doing
> >both. Does one need to only do one or the
> >other? Thanks for any input.
> >
> >--
> >David F. Newman
> >Oracle DBA/Unix admin
> >dnewman_at_ourvillage.com
>
> I would prefer option 2)
> Oracle doesn't 'see' any hardware level mirroring, so if you loose
> that redo log file, it doesn't know about the existence of the mirror.
>
> Hth,
>
> Sybrand Bakker, Oracle DBA
>

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Before you buy. Received on Thu Oct 21 1999 - 09:52:17 CDT