Risc System/6000

[Piercarlo Grandi]

In article <EMV.90Feb20220637 at duby.math.lsa.umich.edu> emv at math.lsa.umich.edu (Edward Vielmetti) writes:
  
  [ disk options on the RS/6000
  
  aha, it's an esdi drive that's built in.  I wondered.
  
  23ms, 1.3MB/sec transfer is wimpy for a fast machine.
  In this configuration the machine is going to be seriously
  i/o bound, without a doubt.

Pah. The bottleneck is the filesystem, unless you do asynch io via a raw
device. You cannot get more than 600KB per second out of the filesystem in
the best of circumstances, and even that is only achieved, as far I know, by
the MIPS UNIX. Others top out at around 300KB per second.

Better seek times improve things a bit. Multiple drives, with overlapped
seek and transfer, improve things much more for a timeshared system.  It is
here, and not in higher transfer rates (or even seek times) that SCSI wins
over ESDI. But the advantage is nonexistent if you have only one drive.

If your only worry is single task fast transfer rate (signal/image
processing), be prepared to implement something like the Amoeba or Dartmouth
or Cray file systems.

The problem is software, not hardware.
-- 
Piercarlo "Peter" Grandi           | ARPA: pcg%cs.aber.ac.uk at nsfnet-relay.ac.uk
Dept of CS, UCW Aberystwyth        | UUCP: ...!mcvax!ukc!aber-cs!pcg
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