On Wed, 26 Oct 2005, Brent L. Bates wrote:

>      I'm having problems writing and reading from an Sony AIT-3 SCSI tape
> drive.  After boot up, I can write to the tape drive and read from it.
>  However, the next time I try to write to the tape drive, it fails.  I've
> found the following in the system logs at the same time of the failures:
>
> 	kernel: st: failed to enlarge buffer to 1048576 bytes.
>
>      I've done some Google searching and have found a number of posts with the
> same problem, but I couldn't find any solutions.  Anyone have any suggestions
> on how to fix this problem?  Rebooting the machine after ever backup isn't a
> good solution at the moment.  Any help greatly appreciated.  Thanks.
>
    Since nobody has given a satisfactory solution, I'll suggest something
perhaps less unsatisfactory than rebooting after every backup.
    You could try removing the st module and reinstalling it:

rmmod st
modprobe st

after which rewinding the tape should get it into a known state.
If that doesn't work, it probably also won't work to remove and
restore single scsi devices, but here's how you can try it:
    Look in /proc/scsi/scsi.  On my computer I see a line like
 Host: scsi0 Channel: 00 Id: 04 Lun: 00
meaning the device is at host, channel, id, lun = 0 0 4 0; so it
can be removed and added back with commands

echo "scsi remove-single-device 0 0 4 0" > /proc/scsi/scsi
echo "scsi add-single-device 0 0 4 0" > /proc/scsi/scsi

and then rewound to get it into a known state.