On Tue, 27 Jun 2006 [EMAIL PROTECTED] wrote:
>
> >This is getting pretty picky. You're saying that ZFS will detect any
> >errors introduced after ZFS has gotten the data. However, as stated
> >in a previous post, that doesn't guarantee that the data given to ZFS
> >wasn't already corrupted.
>
> But there's a big difference between the time ZFS gets the data
> and the time your typical storage system gets it.
>
> And your typical storage system does not store any information which
> allows it to detect all but the most simple errors.
>
> Storage systems are complicated and have many failure modes at many
> different levels.
>
> - disks not writing data or writing data in incorrect location
> - disks not reporting failures when they occur
> - bit errors in disk write buffers causing data corruption
> - storage array software with bugs
Case in point, there was a gentleman who posted on the Yahoo Groups solx86
list and described how faulty firmware on a Hitach HDS system damaged a
bunch of data. The HDS system moves disk blocks around, between one disk
and another, in the background, to optimized the filesystem layout. Long
after he had written data, blocks from one data set were intermingled with
blocks for other data sets/files causing extensive data corruption.
I know this is a simplistic explanation (and perhaps technically
inaccurate) of the exact failure mode - but the effects were that a lot of
data was silently corrupted and went undiscovered for several days.
.... snip .....
Al Hopper Logical Approach Inc, Plano, TX. [EMAIL PROTECTED]
Voice: 972.379.2133 Fax: 972.379.2134 Timezone: US CDT
OpenSolaris.Org Community Advisory Board (CAB) Member - Apr 2005
OpenSolaris Governing Board (OGB) Member - Feb 2006
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