Re: Badness in scsi_single_lun_run at /root/scsi/scsi_lib.c:344

[Willem Riede <wrlk@riede.org>]

On 2004.01.28 12:53, Patrick Mansfield wrote:
> On Wed, Jan 28, 2004 at 12:36:09PM -0500, Willem Riede wrote:
> > On 2004.01.28 11:41, Patrick Mansfield wrote:
> 
> > > Do you know if the single lun code is for performance, or because of
> > > hardware limitations - that is we don't want a disc change between IO, or
> > > does the device just fail?
> > 
> > In the case of the NEC PD/CD, it is a hardware limitation. You can only
> > have one disc inserted at a time, either CD or PD. Mixing IO will fail
> > for the absent media type.
> 
> BTW what is PD?

PD stands for PowerDrive, it uses 650MB (CD size) cartridges that Panasonic
invented before there were writable CDs. I assume they're a type of magneto-
optical device.
 
> So there is one physical drive that can hold one disc, and it can only use
> the LUN associated with the disc that is currently in the drive; and reading
> or accessing the wrong LUN will always fail?
> 
> We don't need single_lun code for that, we can just let the IO fail, right?

That would be no problem. All the single-lun code does is delay the inevitable:
if I address the /dev/scdX which corresponds to the /dev/sdY that's the PD disk
when it's loaded, it _will_ fail (after all IO to the PD's lun finishes).

> I assume there are other single_lun devices that automatically change discs.

Yes, there would be, like CD changers. (That reminds me, I've got one of
those lying around too - I just don't remember how broken it was when I
removed it...)

Regards, Willem Riede.