[1394] in linux-scsi channel archive
Re: looking for a write-protected SCSI disk
daemon@ATHENA.MIT.EDU (Tom Zerucha)
Thu Feb 6 11:33:21 1997
Date: Thu, 6 Feb 1997 11:04:43 -0500 (EST)
From: Tom Zerucha <root@deimos.ceddec.com>
Reply-To: tz@execpc.com
To: Jim Van Zandt <jrv@mbunix.mitre.org>
cc: linux-scsi@vger.rutgers.edu
In-Reply-To: <199701171912.OAA23584@mbunix.mitre.org>
One thought given the source availability of Linux...
You should be able to modify the kernel source to create a read
only version of the sd module, so you can load sd_ro.o by default, but
load sd.o (which you can keep encrypted or on a floppy, etc.) when you
need to write. In sd.c, in sd_open, there is a routine mentioning an
write protect tab. I think if you simply moved the logic to the top of
sd_open, e.g.
if ( (filp->f_mode & 2) )
return -EROFS;
it would function as a write protect - I would note that Jaz and Zip
drivers are functionally software write-protect, so I don't know what
constitutes hardware v.s. software write protection.
I have an external disk/cdwriter that I use an APS 50 pin scsi terminator.
I can unplug the drive and leave the terminator on. It claims to be an
active terminator, so doesn't have to be at the ultimate end of the chain.
The big centronics type connectors should not have a wear problem, but if
you are concerned, get two gender changers and unplug between them.
On Fri, 17 Jan 1997, Jim Van Zandt wrote:
> For some of my projects, I am required to either disconnect or
> hardware write-protect all the normal storage on my machine. To date,
> I have been using dual 230 MB Iomega Bernoulli disks which I can
> remove. (I substitute special disks for those projects.) However, I
> am running out of space for my regular projects. I got an Iomega jaz
> drive, but it is developing enough media defects that I don't trust it
> as a primary storage device (however, that's a separate subject). So,
> I am looking for other options:
>
> Can anyone suggest a SCSI disk drive (either internal or external)
> that has a write protect switch?
>
> How about an external drive that can be turned off but still leave the
> bus properly terminated?
>
> How about an external drive that can be easily disconnected? I am
> somewhat worried about connector wear on conventional cables. Are
> there such things as ZIF (zero insertion force) SCSI connectors?
>
> Thanks in advance for any pointers.
>
> - Jim Van Zandt
>
>
tz@execpc.com
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