Subject: Re: various scsi questions
To: Dante Profeta <>
From: Allen Briggs <>
List: current-users
Date: 02/08/2000 18:07:22
> > 2) with a dual-channel scsi board, do we have twice the bandwidth (i.e. can
> >    the controller manage I/O from both channels at the same time) ?
> Yes

This depends on the host bus.  I think that 32-bit PCI has a theoretical
max of about 132 MB/sec, so if you have two LVD controllers running at
their theoretical max, you've outstripped the PCI bus.  Now if the PCI
bus is clocked higher or if you have two controllers on different
busses, you may be able to run them both at full throttle.  I dunno.
Measuring bandwidth on my 550 MHz K7 (Biostar m.b.) with a very

    dd if=/dev/zero of=/dev/null bs=10240k count=100

we see something like 174MB/sec bandwidth:

    100+0 records in
    100+0 records out
    1048576000 bytes transferred in 6 secs (174762666 bytes/sec)

This doesn't seem to leave a lot of room over 160 MB/s theoretical
max from the dual LVD channels (and isn't enough for two wide-open
PCI busses).

The Alpha servers probably have much better memory bandwidth and
the I/O infrastructure seemed a lot nicer when I was poking around
the alpha web pages (esp. on the 8200 :-)...