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From: sgf@cfm.brown.edu (Sam Fulcomer)
Newsgroups: comp.sys.sgi,comp.periphs.scsi
Subject: Re: < Connecting Fujitsu M2266SA to SGI SCSI (SOLVED) >
Message-ID: <77003@brunix.UUCP>
Date: 29 May 91 15:43:10 GMT
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In article <106450@sgi.sgi.com> jeremy@perf2.asd.sgi.com (Jeremy Higdon) writes:
>
>This disk (2266SA) on a 4D/200 (and up) with PowerChannel (IO3) or 4D/25
>or 4D/35 should get 2.1 or 2.2 MB/s through the filesystem.  On a

Well, given a gentle enough test, perhaps (but I'd be more inclined to
believe 2.0MB/s through the EFS even with a gentle test...). The 
theoretical maximum sustained transfer rate for the drive should be 
a bit less than 2.5MB/s (the speed of the media under the head), and 
once you drop in switch time, seeks and rotational latency, the rate 
drops a bit more.

By a gentle test I mean reads of big chunks from a fairly contiguous
file. The EFS is great for big chunks, however once the chunk 
size drops the FFS becomes a more efficient beast..

I'd think a more realistic expectation would be 2MB/s for reading
big chunks of file with fat extents. 1.6MB/s ought to be about right
for mixed r/w in large chunks, and 2.2MB/s for reading from rdisk.
Mixed r/w's of small chunks can get a little ugly...


-- 
_/**/Sam_Fulcomer	sgf@cfm.brown.edu	What, me panic: uba crazy

Associate Director for Computing Facilities and Scientific Visualization
Brown University Center for Fluid Mechanics, Turbulence and Computation