Alan Cox wrote:
>
> > > 1) Read and write errors should be retried at least once before kicking
> > > the drive out of the array.
> >
> > This doesn't seem unreasonable on the face of it.
>
> Device level retries are the job of the device level driver
>
> > > 2) On more persistent read errors, the failed block (or whatever unit is
> >
> > Generally, it is a good idea to try to rewrite (assuming the original data
> > can be recovered via another method) as sector. If we were really good, we
> > would run a short (changing random) pattern test on the sector before the
> > rewrite to determine whether sparing would be a good idea. Micro defects or
>
> Twenty years ago maybe. Nowdays your drive does all that for you and a
> rewrite will cause a block realloc from the spare list
>
I believe that we were discussing the case when an error made the data
unrecoverable except through RAID reconstruction. The drive does not
handle all cases. (Quantum supports reallocating sectors with
uncorrectable errors through their Special Function Control Page, but
that is not a general approach due to the obvious problems that can
cause.) So, let's say that we have data on one drive that is
unrecoverable and the RAID reconstructs the data, we haven't lost
any data, but under normal default drive setup the sector will not be
reallocated. If testing the failing sector is too much effort, a
simple overwrite with the corrected data, at worst, improves the
chances of the drive firmware being able to reallocate the sector.
This works just fine when you have complete faith in error detection
and correction.
--
Dan Jones, Manager, Storage Products VA Linux Systems
V:(510)687-6737 F:(510)683-8602 47071 Bayside Parkway
[EMAIL PROTECTED] Fremont, CA 94538
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