Date: Fri, 29 May 1998 10:32:50 -0400 From: sbabkin@dcn.att.com To: hackers@FreeBSD.ORG Subject: What to do with this thing ?! Message-ID: <C50B6FBA632FD111AF0F0000C0AD71EEFF8AF1@dcn71.dcn.att.com>
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Hi!
I have brought the SCSI-over-FastEthernet project to the working
prototype stage. And that brought a big question, what to do with
it ? Actually, there are three questions that need further explanation.
But first I shall explain the project, its purposes and
weaknesses. The idea is to tunnel
the SCSI transfers over the FastEthernet thus extending the
possible maximal cable length dramatically. The configuration would
look like:
SCSI Ethernet SCSI
(host)====(converter,master)--------(converter,slave)====(disk)
any FreeBSD FreeBSD any
Using split SCSI transfers and tag queuing allows to make
this kind of configuration rather efficient.
Why would anyone want an extension of this kind ? There exists
a class of paranoia requiring the master and backup
servers be located as far from each other as possible to
protect from disasters like fire. Sure, the automatic fire fighting
systems do exist but would a computer work soon after a freon
bath or covered by lots of dust from smoke generators ?
The company where I worked earlier was infected by this kind of
paranoia and we had to break the high availability cluster
to break up the servers. And I know a whole class of companies
in Russia to which this paranoia is inherent. A nice solution
would be to use configuration like this:
SCSI Ethernet SCSI
(host)=====(converter)-----(converter)=====(backup host)
| |
(disks) (disks)
mirror 1 mirror 2
thus having the backup host and the second copy of data
in a supposedly safe location and electrically disconnected
from the master host.
Possible variations may include using the slave part of converter
as the disk box as well, SCSI ID/LUN translations in converter,
striping, load balancing over several Ethernet connections,
mirroring done inside the converter and so on.
So, about 1.5 years ago I have started this project as commercial
with backup solution of converting it to non-commercial :-)
Many things occurred since then, there were lots of organizational
problems and since I came to US over half a year ago it was
in comatose state at all. Recently I bought a computer and
finally finished the working prototype.
Since the start of project the Fibre Channel technology became
reality, absolutely superior to this project, although, may be,
a bit more expensive. And I absolutely don't know anything about the
typical paranoias in US companies.
So, the first question is: does anybody see any commercial perspectives
for this project ? May be in the low-end server market ? May be,
for non-Unix servers ? If yes, I would like to hear any offers :-)
The second question is: does anybody see any usefulness of this
project in whole as free software, a FreeBSD-based application ? Can it
benefit the FreeBSD project in some way ?
The third question is about using parts of this technology in FreeBSD.
Such as a generic target SCSI driver, a SCSI disk device emulator that
can be useful for SCSI driver debugging, a pseudo-SCSI device that
can wrap the commands to some handler, an IP-over-SCSI implementation.
The last one may be used, for example, as a very fast 40MB/s or
80MB/s (with Ultra-2 Wide SCSI, peak raw throughput) network for
a distributed computing cluster or a kind of a "backplane" for
a router based on such a cluster. With two Ultra-2 Wide SCSI
buses the raw peak bandwidth of this backplane would be 1.2Gbit/s :-)
Does anybody has any ideas or wish lists ?
-Sergey Babkin
babkin@bellatlantic.net
sab123@hotmail.com
sbabkin@dcn.att.com
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