Summary: About SCSI...

From: Rafael Napoles Rodriguez (rnapoles@reduno.com.mx)
Date: Fri Jul 11 1997 - 10:27:20 CDT


Hello sun managers:

***** My original post was:
>
> I have a sparcstation20 with a tape unit and a external hard disk
> connected to the bus SCSI (SCSI II). I want to add other hard disk, but
> it has a old connector (SCSI I). Do you know of any problem (performance,
> etc.) if i mix these different types of connectors? Can you give me any
> reference about this topic?
>

        In general, there are a few problems with this type of implementation,
it must operate normally. Bismark Espinoza recommend that i connect the
SCSI I device to the end of the SCSI chain. I got only this reference in
the WWW:

   http://www.stokely.com

        Unfortunately, I haven't got the SCSI cable for test. :(

***** Thanks you to:
 
foster@bial1.ucsd.edu
Bismark Espinoza <bismark@alta.Jpl.Nasa.Gov>
Tariq Ahmed <tahmed@viper.istar.ca>
Jim Harmon <jharmon@telecnnct.com>
Jens Fischer <jefi@kat.ina.de>
Mariel Feder <unix.support@central.meralco.com.ph>

***** These are the answers received:

foster@bial1.ucsd.edu wrote:

You might want to look at Celeste Stokeley's web page:

        http://www.stokely.com/

I don't think there are any performance hits when mixing these types
of connectors, but please don't quote me on that!

-------------------------------------------------------------------------------

Bismark Espinoza <bismark@alta.Jpl.Nasa.Gov> wrote:

It will work.
But you may get scsi errors.
Put the scsi-1 device at the end of the chain.

-------------------------------------------------------------------------------

Tariq Ahmed <tahmed@viper.istar.ca>

        As long as you have no SCSI ID conflicts, SCSI is downward
compatible. So you should have no problems.

-------------------------------------------------------------------------------

Jim Harmon <jharmon@telecnnct.com> wrote:

SCSI 1 is an 8-bit 10MB/s bus.

SCSI 2 is also 8-bit 10MB/s.

FAST SCSI2 is 8-bit 20MB/s.

If you have a fast-scsi system, you will slow your disk access about 25%.

If you have slow scsi already, you won't notice anything.

You should have NO bad problems.

-------------------------------------------------------------------------------

Jens Fischer <jefi@kat.ina.de> wrote:

the thing to look at is the disk, not the connectors. You can find many
SCSI II disks in enclosures with SCSI I connectors, which should be no
problem
at all if you have a matching cable handy. The usage of SCSI I disks within
a SCSI II chain should also work as the SUNs are negotiating with every
single
SCSI device in order to find a speed and transfer mode which is supported by
the device. As this works on a per device basis there should be no
performance
impact for the SCSI II devices if you add a SCSI I device to the chain.

-------------------------------------------------------------------------------

Mariel Feder <unix.support@central.meralco.com.ph> wrote:

We have that working without any problem.
The only thing you need is a cable with each connector
on each end, and it should work transparently.

***** Greetings!

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           * Ing. Rafael Napoles Rodriguez *
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