Re: San & single point of failure

From: Mark Brinsmead <>
Date: Tue, 18 Nov 2008 19:30:20 -0700
Message-ID: <>

What? Why beware of that? In some places I have been, this might be the * good* stuff! :-) (And yes, I *do* subscribe to BAARF.)

What you *really* need to worry about is the situation where some idiot gives you a RAID-1 where the two mirrored volumes are at either end of the *same disk*! Not only is there no protection, but the performance is the stuff of nightmares.

Sadly, many RAID vendors actually claim that RAID-5 (well, *their* RAID-5, anyway) is just as good as RAID-1. Or better. And many storage administrators will believe them. Often there is nothing you can do about this.

Happily, I have yet to encounter a storage vendor who claims that it is a * good* idea to do RAID-1 with two slices of the same physical device. But every now and again, you may see a storage administrator do it. Usually by accident, I hope. Thankfully, I have never encountered this one first hand, but I've seen close. :-)

On Tue, Nov 18, 2008 at 9:10 AM, QuijadaReina, Julio C <> wrote:

> Beware also of SAN administrators who setup RAID 5 and later give that
> storage to DBA's for their databases. It does not hurt to double check what
> kind of underlying RAID they've got for you.
> Julio
> <...snip..>

-- Mark Brinsmead
  Senior DBA,
  The Pythian Group

Received on Tue Nov 18 2008 - 20:30:20 CST

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