In message <Pine.ULT.4.02A.9808160843160.9095-100000@vali.stanford.edu>  "Dr. Bill Studenmund" wrote:
> On Sun, 16 Aug 1998, Stefan Grefen wrote:
> 
> >   2) Scsi:
> >     If you rescan the SCSI bus and the user has switched the scsi-id of
> >     two devices what do you do? 
> 
> You tell the user they're an idiot. You sould not be changing the ID of
> live devices.

This can happen faster than you may think, just take one of the tape or
OD librarys where you can change the SCSI ID's from the frontpanel.
If you power cycle them before you store the stuff to NVRAM they'll 
change SCSI'ID.
The problem is it can happen, and Murphy will it happen at a time 
were the damage is huge :-)))

> 
> >     Assume it's to tape drives? 
> >     I know you shouldn't do it, but Joe blow will do it and scream if
> >     his date goes south.
> > 
> >     More common: you turn of one of your disks/tapedrives. 
> >     Are you going to renumber the remaining ones?
> 
> One thing to note here is that the recomended practice (which I'll admit I
> ignore) is to wire down your known devices. So for instance sd2 will
> always be target 4 on scsibus 0, regardles of what's turned on or off.
> 
> I agree that we have a ways to go on being able to remove devices, but I
> think we will be able to require a certain amount of user savvy to make it
> work.

I hate rebooting my machine to turn on/off a tape or move it to another machine.
There is only one thing missing in NETBsd, a command to start/stop a scsi-bus,
and you could revommend a save method for switching devices online.
(eg. Unixware 7 has this now)

I do work for a company that counts uptime in month and years, so my
opinions may be biased :-))

Stefan

> 
> Take care,
> 
> Bill
> 

--
Stefan Grefen                                Tandem Computers Europe Inc.
grefen@hprc.tandem.com                       High Performance Research Center
 --- Hacking's just another word for nothing left to kludge. ---