Re: San & single point of failure

  • From: "Mark Brinsmead" <pythianbrinsmead@xxxxxxxxx>
  • To: QuijadJC@xxxxxxxxxxxxxxx
  • Date: Tue, 18 Nov 2008 19:30:20 -0700

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

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 <
QuijadJC@xxxxxxxxxxxxxxx> 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

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