Odd behavior after installing a tape drive

Polytropon freebsd at edvax.de
Mon Jul 20 04:22:57 UTC 2009

On Sun, 19 Jul 2009 21:43:29 -0600, Tim Judd <tajudd at gmail.com> wrote:
> I'm no expert on tape drives either, but I was sure that "losing a
> SCSI device" is a bad thing for SCSI -- think of it as an IDE drive.
> you don't just go pulling power or data from a running, booted
> computer.

With SCSI, "hot plug" is usually not that problematic as with
"modern" ATA and SATA on the PC. Anyway, using

	# camcontrol stop <unit>

before switching off or detaching a SCSI component is often a
good idea.

> All the devices in a computer are on, stays on, until the system shuts down.

SCSI allows you to have "internal devices" outside the computer,
connected with a cable. In principle, it doesn't even matter if
a hard disk is inside the computer or outside, same for optical
disc drives, tape drives, and even scanners. "Hot plug" has always
been a nice feature of SCSI, even 10 or more years ago, where
you couldn't imagine something similar in the PC world.

> The PTY/SCSI subject of your email should be unrelated, but a abruptly
> missing device is never a positive outcome for an OS.  Think about the
> old "removing a mounted USB drive = panic" issue we've dealt with for
> years.

Or /dev/mem: device disappeared. :-)

> I am questioning your reasoning behind turning off a tape drive on a
> live system.  I would never recommend that.

As I said, if you do it "the SCSI way", it's completely unproblematic.

>From Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...

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