On Fri, 27 Jun 2003 at 9:40am, Russell Adams wrote

> I'm having repeated problems with my tape changer and the sg device.
> 
> I'm running a Dell Powervault 120T (DLT7000 w/ 7 tape changer) on an
> adaptec (aic7xxx driver) card.
> 
> Every time I load a tape using mtx, subsequent calls to mtx report:
> 
> cannot open SCSI device '/dev/sg0' - No such device or address
> 
> /dev/sg0 still exists, but I can't seem to talk to the changer
> anymore. I can talk to the drive itself however.

Can you actually write to the drive?

> The only fix I've found for this is to rmmod all the scsi drivers
> (st,sr_mod,sg,aic7xxx) and then insmod them again.

This sounds suspiciously like either bad hardware or a bad SCSI chain.  
Are you sure everything is terminated properly?  How's your cable length?
Does it work on another machine or with a different SCSI card?  What color 
was the goat?

-- 
Joshua Baker-LePain
Department of Biomedical Engineering
Duke University