Re: Do we need multiple REDOLOG member if it is already on SAN box?

From: joel garry <>
Date: Mon, 2 May 2011 09:54:37 -0700 (PDT)
Message-ID: <>

On May 2, 1:20 am, Noons <> wrote:
> On Apr 30, 4:33 am, charles <> wrote:
> > I have a question.  I have a Oracle database, everything is
> > on SAN storage ( Raid 10). When i am asking for another LUN for 2nd
> > redolog members, he told me we have already mirrored for u at the san
> > level.  So he thinks it is not necessary to have two members of
> > redolog in each group.
> > Could somebody share some idea with me?
> Been discussed many times.  Recently at the oracle-l list the
> consensus even from the Oakies is do not do mirroring twice.  Either
> do Oracle multiple members, or do SAN-based mirroring.  Doing it twice
> achieves really nothing other than slowing things down.  One or the
> other, not both.
> Given that the days SANs lost data are long gone (not a single data
> failure in over 4 years now of 12TB of I/O per day) we've gone for SAN-
> based last year.  Fine so far and archived redo logs copied to DR site
> every two hours gives me even more comfort.

Would you really come to the same conclusion without DR? In my view, applying the archived logs to a standby is the only way to know the redo stream is at least non-corrupt, and if you don't have that, you want to have additional checks elsewhere.

> YMMV based on how paranoid you are.

You may be over-estimating everyone else's ability because your ship is so tight! I'm not running standby now because a particular array works with two versions of hp-ux, but not the version in between, and no one knows why. SAN's are not magic, they fail when their components get old or their environment changes. The failure may lack grace.


-- is bogus.
Not paranoid enough:
Received on Mon May 02 2011 - 11:54:37 CDT

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