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From: braner@batcomputer.UUCP
Newsgroups: comp.sys.atari.st
Subject: Re: Disk R/W times for large files
Message-ID: <1643@batcomputer.tn.cornell.edu>
Date: Wed, 8-Jul-87 15:06:44 EDT
Article-I.D.: batcompu.1643
Posted: Wed Jul  8 15:06:44 1987
Date-Received: Sat, 11-Jul-87 15:16:04 EDT
References: <383@uop.UUCP> <781@atari.UUCP>
Reply-To: braner@tcgould.tn.cornell.edu (braner)
Organization: Cornell Theory Center, Cornell University, Ithaca NY
Lines: 18
Summary: Use a _moderate_ (or larger) buffer

[]

Greg didn't say what program copied the files.  I _guess_ it's the Gulam
'cp' command.  I don't know how it does it, but apparently not well.
500K in 36 seconds is about 14 Kbytes/sec.  The theoretical max is 22.5
Kbytes/sec (one track per rev).  My boot disks actually achieve that
when copying into the RAMdisk using 'Autodisk' (and the floppy is 'fast'
formatted).  Autodisk copies with a _huge_ buffer (the whole RAMdisk).
"Twister" formatted disks read about 80% as fast, and standard disks
about half as fast (i.e., twice as slow).

But my experiments (when modifying microEmacs, etc) show that, with typical
text files (<50K), a buffer of 9K (one DS track) yields a performance that
is very close to that of larger buffers.  That is with standard
("slow") formatted disks.  (The performance gradually levels off as you
increase the buffer size through 4.5, 9 and 18K.)

- Moshe Braner