🚀 go-pugleaf

In article <348c422b.31666353@news.demon.co.uk>
           bob@lintilla.demon.co.uk "Bob Cousins" writes:

">Workstation performance is dominated by sustained transfer rate and not
">access time.
"
"I think that's completely untrue. Only in very few situations do you get
"conditions where sustained transfer rate would be dominant. [snip]

    I've been reading the part of this thread to do with access
 rather than EIDE/SCSI in a somewhat bemused fashion.  Let's skip
 the parts that are to do with stand-alone systems (most of the
 posters are discussing servers), and think about the dominant
 factors in a network data transfer.  All this work was done in
 CompSci departments in the 1970s (if not 1960s).

    It is really not safe to say that any one factor is dominant
 in determining average transfer-rates, except in tightly defined
 circumstances.  I have not noticed a single post discussing the
 effect of two simultaneous transfers (of different data), or of
 network bandwidth limitations, etc.  The effects of
 'disk-thrash', 'ethernet degradation' etc can be massive.
 (Frinstance, in the early days of classroom networks, where a
 single pupil could download the software in 20 seconds, it could
 take 30 minutes for a class of 10 to do so if all started
 simultaneously.)

    In general terms, in any situation where there are likely to be
 simultaneous transfers going on, putting reasonable figures into
 the calculations is likely to show that transfer-rate will be
 improved more by massive buffering, read-ahead logic and large
 logical packets on the LAN than by speeding up raw disk-to-RAM
 transfer rate.  The concept is to do quite a lot of one thing
 before you switch to another, rather than switching frequently.
 The major loss of time is associated with changing from one thing
 to the next.  (Consider the well-known effect on car-traffic-flow
 of making traffic-light cycle-times longer.)

    Where's my flame-proof vest?

                                                Chris K.
-- 
Chris Kennington (newshound)                        01491 574065
  You can mail me with suitable modifications to header-addresses,
   or to "chris <at> inf-eden.demon.co.uk", replacing the <at>.