----- Original Message -----
From: "David VanHorn" <[EMAIL PROTECTED]>
To: "Protel EDA Forum" <[EMAIL PROTECTED]>; "Protel EDA Forum"
<[EMAIL PROTECTED]>
Sent: Tuesday, May 07, 2002 10:38 AM
Subject: Re: [PEDA] recovering data


>
> >
> >Stop! Don't confuse the terms!
>
> I'm not confused.
>
> >A raid system is definitly NOT a backup, it's something like a fail safe
> >system!
> >It protects ONLY against hardware failture and can't replace a backup
system.
>
> Does it protect against failures of the raid controller?
> Does it protect against the OS instructing the controller to destroy your
data?
>
> >With a raid level 5 it is possible to work further if one (and only one
of
> >at least three) of the hard drives fails.
>
> So you cube your odds of having a drive fail, to protect yourself from
that
> failure, assuming the OS or the applications don't barf all over the data
> first?
>


Not to be nitpicking and generally agree with you Dave, however, there is
one single issue - you are replacing a catastrophic failure mode with a
recoverable error by using RAID . You're cubing your odds of having a
(recoverable) error vs. the odds of having a catastrophic non-recoverable
error . Which one do you prefer ? It makes the failure more of a warning
sign than a terrible event . Replace the faulty drive before you have more
warning signs and you're ok.

Of course, there's still the question of the probability of one of those
recoverable errors to be not so recoverable after all , and if it's more or
less probable than the unrecoverable error of the single drive we started
with ;)

regards,

Matt Tudor, MSEE - RF Design
http://www.gigahertzelectronics.com



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