Re: [PATCH as468] Retry supposedly "unrecoverable" hardware errors

[Douglas Gilbert <dougg@torque.net>]

Alan Stern wrote:
> James:
> 
> This is an updated and unmangled version of the patch sent in by Martin 
> Peschke.  Apparently some drives report Hardware Error sense for 
> problems which do improve after retrying, so the patch retries these 
> supposedly "unrecoverable" errors for such devices.

Recent SPC-3 and SBC-2 drafts treat the sense keys of
MEDIUM ERROR and HARDWARE ERROR in a similar way.
Both can return an "info" field which has the same
meaning (lba of first failure). The distinction is that
MEDIUM ERROR is a little more precise (at least for
magnetic rotating media) **. For flash ram the distinction
is moot.

I believe MEDIUM ERROR and HARDWARE ERROR should be
treated the same way in scsi_check_sense() (i.e.
both return NEEDS_RETRY). That way an extra black list
category is avoided.


** HARDWARE ERROR is returned in cases of self diagnostic
failure and lack of available blocks for reassignment.
It seems valid for a device to return a HARDWARE ERROR
sense key both for these cases and unrecoverable data
errors (and ignore MEDIUM ERROR).

Doug Gilbert