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

From: Noons <>
Date: Mon, 2 May 2011 21:30:02 -0700 (PDT)
Message-ID: <>

On May 3, 2:54 am, joel garry <> wrote:

> 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.

If you want to have a non-stop HA system, that is a totally and completely
different proposition from a normal operational system.

For the latter, one type of mirroring is plenty enough. Assuming of course the minimum care has been taken with backups, archived redo logs, etcetc. The redundancy and data verification mechanisms in-built into Oracle and/or SAN hardware/software are plenty enough to take care of any remaining problems.

Of course if you want the former and you want to have absolute confirmation that no matter what comes, hell or sunshine, you can always get the last closed transaction, then be prepared to pay the price. It is however very high, in both performance and cost.

I find very few places nowadays - other than military or high-end financial - that NEED that degree of protection AND are willing to pay for it.

> > 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.

They are not magic but they are by far the best current compromise between reliability, performance and price. Because I can't afford better bang with my buck, I'm happy with them and their demonstrated level of reliability so far.

Given that I also have a full online backup and archived redo log facility to back up the SAN-based DR replication, I'm sufficiently covered - within my cost-bracket - to ignore the need to mirror the mirrors.

Horses for courses. Received on Mon May 02 2011 - 23:30:02 CDT

Original text of this message