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From: smvorkoetter@watmum.UUCP
Newsgroups: comp.sys.ibm.pc
Subject: Re: UNIX more fragile than MS-DOS files?
Message-ID: <1822@watcgl.waterloo.edu>
Date: Mon, 21-Sep-87 09:24:39 EDT
Article-I.D.: watcgl.1822
Posted: Mon Sep 21 09:24:39 1987
Date-Received: Tue, 22-Sep-87 06:40:09 EDT
References: <174@westmark.UUCP->
Sender: daemon@watcgl.waterloo.edu
Reply-To: smvorkoetter@watmum.waterloo.edu (Stefan M. Vorkoetter)
Organization: U. of Waterloo, Ontario
Lines: 33

In article <174@westmark.UUCP->  dave@westmark.UUCP (Dave Levenson) writes:
-> UNIX files may sit in kernel buffers long after the process who last
-> touched the file has terminated.  The sync command flushes the
-> buffers, but unless you're planning to shut down, who uses it?

In the UNIX course I took, I was taught that the buffers get flushed
every 30 seconds or so.  I guess this is by the daemon you mention
below.

-> MS-DOS, also, buffers files, but flushes the buffers associated with
-> any given file when the file is closed.  If you shutdown without

MS-DOS uses write through buffers.  When you read a sector, it will check
if the sector is in a buffer, and read it from there if it is.  When you
write a sector, it writes straight to the disk (AND the buffer).  The file
will only be trashed if a crash occurs during the write.

-> exiting the application, MS-DOS files get trashed, too. The apparent
-> robustness of MS-DOS files comes, I think, from the user's tendency
-> to exit the application, even if he doesn't shut down the system,
-> before powering down.  MS-DOS has no shutdown command, so no need to
-> learn to use it.
-> 
-> Some versions of UNIX run a daemon which syncs the filesystem
-> periodically.
-> -- 
-> Dave Levenson
-> Westmark, Inc.		A node for news.
-> Warren, NJ USA
-> {rutgers | clyde | mtune | ihnp4}!westmark!dave

Stefan Vorkoetter
University of Waterloo