[ILUG] SCSI questions

[Kenn Humborg]

> > 1. Is it safe to connect/disconnect a SCSI cable from
> >    a powered-up device (either host adapter or disk/tape
> >    drive)?
> >
> > 2. Is it safe to power up/down an external SCSI device
> >    while the host adapter is powered?
>
>    with tape drives and so long as nothing is going down the line, yup.
>    I've done this a few times on hp machines, Just be very carefull.
>    The same could be said for disks as long as they're not mounted etc...
>    Just be carefull.  Make sure theexternel device was in the same state
>    before you disconnected it.  If its a tape drive, then things
>    should be more redundant.

Sounds OK.

> > 3. Is the SCSI command set 'remotable'?  Could you, in
> >    theory, write a virtual SCSI port driver that would chuck
> >    the SCSI commands across a network to another machine
> >    which would then put them on a real SCSI bus, and return
> >    the device's response across the net?
>
>   something like a remote device ?  Been done hasn't it ?  I've
>   done this, accessing a /dev/rmt/... device which was on another machine,
>   though  I think it went thru rsh stuff...  Nice idea though.

I'm thinking that the generic SCSI device on Linux (sg, isn't it)
should make a user-land daemon trivial to write.  I already have
stuff that remotes a CD and disk space for VMS to user-land
Linux daemons.  (It's not production-level code.  The data is
just chucked across the ethernet as raw frames.  No IP or TCP
or anything.)

It would be a lot easier to start from this than to do rsh or
rmt (which probably wouldn't fit VMS's ideas about how tapes
are supposed to work).

> > (No 3 is a sick twisted plan for accessing my SCSI devices
> > from VMS even though I don't have a SCSI adapter in the VAX.
> > I do have one in my PC, and writing a SCSI port driver
> > for VMS shouldn't be too hard.  It would certainly be easier
> > than implementing the rmt protocol.)
>
>   Someone got his DECUS license then ?

Yeah.  Buy I can't back up my current VMS installation because
I don't have tapes for the drive in the machine and I don't have
a SCSI adapter to hook up the drive that I _do_ have tapes for.

Arrggghh...

Later,
Kenn