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From: dave@micropen (David F. Carlson)
Newsgroups: comp.sys.ibm.pc
Subject: Re: UNIX more fragile than MS-DOS files?
Message-ID: <377@micropen>
Date: Mon, 21-Sep-87 16:18:07 EDT
Article-I.D.: micropen.377
Posted: Mon Sep 21 16:18:07 1987
Date-Received: Wed, 23-Sep-87 01:45:24 EDT
References: <174@westmark.UUCP>
Organization: Micropen Direct Writing Systems, Pittsford, NY
Lines: 32
Summary: UNIX filesystem is evolving too

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?
> 
> Some versions of UNIX run a daemon which syncs the filesystem
> periodically.
> -- 
> Dave Levenson

DOS keeps in in-core copy of the FAT, which is absolutely analogous to
the in-core copy of the inode table and free list that UNIX maintains.
The question is was means is used to flush them out and how much redundancy
is built in.

Note that FFS (Berkeleys fast file system) has multiple copies of the superblock
information for some fault protection.  Note also that Microport has "hardened"
their filesystem by periodically syncing (I believe maximum sync time is ten
seconds), thus your hard crash can only undo currently open files and those 
closed less than 10 seconds before the crash.  The sync routine is also called
using the <cntl><alt><del> sequence so you reboot with clean volumes.  I have
crashed our Microport systems and have experienced period power failures and
I have found that their file system is not perfect but I claim better than 
normal system5 and Berkeley systems I have used before.  I certainly have had
DOS go "byebye" for some unknown reason and lost files.  At least protected
mode OS's don't go "byebye" with such frequency as a DOS system.

-- 
David F. Carlson, Micropen, Inc.
...!{seismo}!rochester!ur-valhalla!micropen!dave

"The faster I go, the behinder I get." --Lewis Carroll