[5104] in linux-scsi channel archive
Re: Linux as a SCSI _Target_ device?
daemon@ATHENA.MIT.EDU (Tim Smith)
Thu Nov 12 07:05:47 1998
Date: Wed, 11 Nov 1998 23:29:47 -0800 (PST)
From: Tim Smith <tzs@tzs.net>
To: Jeff Noxon <jeff@planetfall.com>
cc: linux-kernel@vger.rutgers.edu, linux-scsi@vger.rutgers.edu
In-Reply-To: <19981110194852.D13054@planetfall.com>
On Tue, 10 Nov 1998, Jeff Noxon wrote:
> Can anyone tell me if it would be possible to make a Linux system appear
> to another system as a SCSI target? I want to RAID 5 a whole mess of
...
> I'm guessing it would be possible with one of the Symbios chips and some
> clever hacking. True/False? Where to start?
I've never looked at the Linux SCSI code, but I've had a lot of experience
with the predecessors of the current Symbios chips (the 53C700, 710, and
720...the company I worked for did most of the SCSI software for NCR
Microelectronics back then), and from a hardware point of view, your
guess is accurate. It doesn't even take clever hacking, because SCSI
target mode is actually *easier* than initiator mode. It is the target
that control a SCSI transaction.
In fact, target mode is easy enough that I managed to get a SCSI RAM disk
working entirely in the 53C7xx scripting language. I had to use a 256
byte sector size, because the chip did not have powerfull enough
arithmetic operators to convert a 512-byte-block count into a byte count,
but aside from that oddity, it actually worked. (I could handle 256 byte
blocks because the necessary shift by 8 to convert could be done with
byte-aligned memory moves).
Anyway, at the SCSI level, you'll have no problems.
--Tim Smith
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