Path: utzoo!utgpu!water!watmath!clyde!att-cb!att-ih!pacbell!ames!ucsd!sdcsvax!cantrell@Alliant.COM
From: cantrell@Alliant.COM (Paul Cantrell)
Newsgroups: comp.os.research
Subject: Re: O/S's using bit maps for free disk block lists?
Message-ID: <4827@sdcsvax.UCSD.EDU>
Date: 31 Mar 88 23:23:17 GMT
Sender: nobody@sdcsvax.UCSD.EDU
Organization: Alliant Computer Systems, Littleton, MA
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Approved: comp-os-research@ucsd.edu

The MASSCOMP unix file system, which was a derivative of the Bell file
system, was modified by Tom Teixeira (now at Stellar) to do bitmap
allocation of file blocks. This was necessary because the system supported
contiguous block allocation (required for the high speed data acquisition).
You could try mailing him at stellar for more information about it.

My experience with his file system was that allocations were very fast,
and the file system throughput was very high. Even when non-contiguous
files were allocated, a side affect of the bitmap allocation was that
the blocks were obtained in sorted order. Even with gaps between some
of the blocks, the locality obtained made for very nice file system
throughput. I can't think of any negative effects of his allocation
method...


					PC