>>kern/3021 describes poor handling of UNIT ATTENTION in the scsi
>>driver.  The sense code handling recently got churned, but I don't
>>think this has been changed.  At any rate, the bug doesn't seem to
>>have been looked at.  (This one includes only skeletal code.)
>
>The real fix for this would be to update sd.c to actually parse errors
>rather than let the (limited) general case suffice. I won't have time
>to do this at present.

I've thought about this somewhat, and I don't think that the low level disk
driver can completely handle this situation.  For instance, if a drive
loses power for some reason and comes back up, you may be able to verify
that it is the exact same drive if it supports the serial number inquiry
page or has a SCSI III WWID, but without a serial number or ID, what do you
do?   Even if you have some identifier, it may not be sufficient for
removable media devices unless the serial number is media specific.  There
are still many common devices that don't have serial numbers (Jaz and Zip
drives come to mind).

I think you have to have some type of generic media "verification" system
in addition to properly handling the sense codes.  NT actually sticks some
kind of identifier in an otherwise unused section of the partition table,
but there may be other ways to handle this and have it work even if a disk
doesn't contain a BSD label on it anywhere.

>-matt

--
Justin T. Gibbs
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  FreeBSD: Turning PCs into workstations
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