Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!ucsd!ucbvax!agate!saturn!moscom!adp@cs.rochester.edu
From: moscom!adp@cs.rochester.edu (Alan Percy)
Newsgroups: comp.os.research
Subject: Re: References for Fault Tolerent, "safe" file system
Message-ID: <7597@saturn.ucsc.edu>
Date: 22 May 89 14:38:51 GMT
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In article <7013@saturn.ucsc.edu> vlohia@orville.nas.nasa.gov (Ved P. Lohia) writes:
>
>I am looking for references regarding fault tolerent, "safe" file system.


When I examined making a "safer" file system that would be
based on a standard operating system, we came up with a rather
simple conclusion:

We where going to use dual hard disks and controllers.  The system
would have the dual media and a driver that would write to both,
but read from only one.  If a media failure was detected the
backup disk would be read from.  The bad track on the primary would
be reassigned and rewritten with data from the backup.

This could be done with only one controller and drive, but keeping
duplicate copies of each track on another platter in the same cylinder.
In our system, halfing the total storage and slowing writes down
was an acceptable trade off to gain reliablility.


-- 
Alan Percy..........................{rutgers,ames,cmcl2}!rochester!moscom!adp