On Wed, Sep 26, 2007 at 04:02:49AM -0400, bob944 wrote:
> Bogus comparison.  In this straw man, that 1/100,000,000,000,000 read
> error a) probably doesn't affect anything because of the higher-level
> RAID array it's in and b) if it does, there's an error, a
> we-could-not-read-this-data, you-can't-proceed, stop, fail,
> get-it-from-another-source error--NOT a silent changing of the data from
> foo to bar on every read with no indication that it isn't the data that
> was written.

While I find the "compare only based on hash" a bit annoying for other
reasons, the argument above doesn't convince me.

Disks, controllers, and yes RAID arrays can fail silently in all sorts
of ways by either acknowledging a write that is not done, writing to the
wrong location, reading from the wrong location, or reading blocks where
only some of the data came from the correct location.  Most RAID systems
do not verify data on read to protect against silent data errors on the
storage, only against obvious failures.

-- 
Darren Dunham                                           ddunham AT taos DOT com
Senior Technical Consultant         TAOS            http://www.taos.com/
Got some Dr Pepper?                           San Francisco, CA bay area
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