Hi,
On Thu, Apr 13, 2000 at 09:18:09AM -0500, Ed Carp wrote:
>
> > Huh? Modern disks do this for you anyway. It is counterproductive
> > for the kernel to try to help, because if the kernel remaps what appears
> > to be a bad block, then you're just duplicating effort. The next time
> > the kernel tries to write to that "bad" block, the disk will have
> > remapped it on its own.
>
> Most modern disks do this for you *transparently* - the driver doesn't even
> see the error, so this does't really apply. If the kernel sees an error, it's
> a real error, as opposed to one that has been remapped.
Not quite. If you get a read error, the drive will do the remapping
for you such that future writes to the same sector will be mapped
elsewhere on disk. However, that transparent remapping cannot, by
itself, restore the contents of the lost sector. The kernel will
still see the read error --- it's only future contents of the same
logical sector which will be remapped.
> Not entirely true in all cases - I've got drives that develop a bad block or
> two every year or so, and they've been in service for at least 3 years.
See above: it's still perfectly possible to get read errors even if
remapping is working perfectly.
--Stephen
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