Path: utzoo!censor!geac!torsqnt!lethe!yunexus!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!dlyons
From: dlyons@Apple.COM (David A. Lyons)
Newsgroups: comp.sys.apple2
Subject: Re: Reordering GS/OS directories
Message-ID: <48800@apple.Apple.COM>
Date: 4 Feb 91 01:04:19 GMT
References: <425@generic.UUCP>
Organization: Apple Computer Inc., Cupertino, CA
Lines: 27

In article <425@generic.UUCP> taob@pnet91.cts.com (Brian Tao) writes:
>From toddpw@nntp-server.caltech.edu (Todd P. Whitesel):
>
>> Since the FST's are assumed to be caching blocks whenever they can (the
>> ProDOS FST does it to directory blocks a lot), it is a very bad idea to
>> perform direct writes to blocks that an FST thinks it has a valid cache
>> copy of.
>
>    Is it not possible to purge or flush the GS/OS cache after a direct block
>write of the boot disk?  That would force the directory information to be
>reloaded from the disk, and nothing would be corrupted.
>
>Brian T. Tao  {taob@pnet91.cts.com} ||  Computer guru?  Someone who got
>University of Metro Toronto         ||  their computer a couple of weeks
>Scarberia, ON, MIC 3A8         *B-) ||  before you did.  (Alvin Toffler)

Flushing the cache doesn't address the problem; the tricky part is when
an FST has its *own* copy of some of the data on the volume.  (You could
call this a "cached" copy, but it's not in the GS/OS Cache.)
-- 
David A. Lyons, Apple Computer, Inc.      |   DAL Systems
Apple II System Software Engineer         |   P.O. Box 875
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My opinions are my own, not Apple's.