[3955] in linux-scsi channel archive
Re: Disconnecting scsi devices
daemon@ATHENA.MIT.EDU (Kurt Garloff)
Tue May 19 18:34:52 1998
Date: Tue, 19 May 1998 18:59:56 +0200
From: Kurt Garloff <garloff@kg1.ping.de>
To: Brendan Miller <brmiller@wco.com>, linux-scsi@vger.rutgers.edu
Mail-Followup-To: Brendan Miller <brmiller@wco.com>,
linux-scsi@vger.rutgers.edu
In-Reply-To: <19980518154421.15998@wco.com>; from Brendan Miller on Mon, May 18, 1998 at 03:44:21PM -0700
On Mon, May 18, 1998 at 03:44:21PM -0700, Brendan Miller wrote:
>
> I have a BusLogic BT-958 for the disks with all my *main* partitions
> (/ /usr /var /usr/local /home /cdrom, etc.), and I have an aha152x for
> my ZIP drive. (Since the ZIP uses that 25pin pseudo-SCSI, I didn't
> want to *infect* my *real* SCSI chain with that. :))
>
> The aha152x support is modularized, so if I don't really want it, or if
> the ZIP isn't connected, I can remove the modprobe in my /etc/rc.d/rc.modules
> and it won't load. I was wondering, then, if I can do the following
> with the machine *ON*:
>
> # rmmod aha152x
> <power down ZIP>
> <unplug ZIP from aha152x>
> <take ZIP to another machine>
> <do stuff>
> <bring ZIP back to Linux PC>
> <reconnect ZIP to aha152x>
> <power up ZIP>
> # modprobe aha152x
>
> If it's the only thing on the bus, it should be fine, no?
>
> If this works, then could I also add/remove other devices the same way,
> so long as nothing on the chain was mounted?
Yes. If it's the only device on the bus you're fine.
If you want to connect it to a working SCSI bus, it's much more risky.
AFAIK, this is not specified in the SCSI spec.
But: I often do hotplug SCSI devices: (T means termination)
-----
----| T |
-----
----- -----
----| T |---| T |
----- -----
----- -----
----| |---| T |
----- -----
Note that there is an intermediate situation when the bus is terminated
twice. This is bad of course, but it is definitely better than having no
termination for some time. I take care not to have SCSI bus activity for
that period of time. After everythingis set up, I use the
"scsi add-single-device" interface to add it to the known devices of my
system.
Disconnecting goes the other way round.
I do NOT recommend to do that; I had no problems yet, but I won't take
responsibility if others do.
--
Kurt Garloff, Dortmund
<K.Garloff@ping.de>
PGP key on http://student.physik.uni-dortmund.de/homepages/garloff
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