SCSI speed with IBM DGVS09U (8 GB) hard drive, Linux

[Albert Max Lai]

On Wed, 6 Jan 1999, Ricky Beam wrote:

> U2 SCSI is LVD -- Low Voltage Differential.  You generally cannot mix LVD
> and non-LVD devices on the same physical cable without causing problems.
> That does not say it cannot be done at all.

Apparently Adaptec says that they can handle it on their U2W cards, but
that is not the issue. 

> As long as all the devices are SE (Singal Ended), then you can put the
> slowest crap SCSI-1 device on the bus with the most modern high speed
> SCSI-3 device.  (That was part of the design spec from the beginning.)
> 20MHz and 40MHz are "Ultra" SCSI speeds (FAST-20 and FAST-40; UltraStor
> holds a TM/patent on "UltraSCSI") and your /proc output indicated ultra
> scsi was disabled.

The setup in questions is a 2940UW, which means that all the devices are
SE and therefore, as you say, can be used in a mixed configuration. So,
one should be reading the higher transfer rates in this setup.

> If in doubt, test the transfer speed with 'hdparm -Tt'
Thanks for the tip.

--
Albert Lai <amlai at columbia.edu>           1018D East Campus
Residential Computer Consultant           411 W. 116th St.
Columbia University                       New York, NY 10027
http://www.columbia.edu/~aml61            (212)853-4854



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