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Ftp from: ftp.ms.uky.edu:/u/ftp/pub/tech-reports/UK/cs/225-93.ps.Z

Tech-report number: 225-93
Date:               January 1993
Title:              The Viva File System
Authors:            Eric H. Herrin II and Raphael A. Finkel
E-mail:		    eric@ms.uky.edu and raphael@ms.uky.edu
Abstract:
        This paper describes the Viva File System or VIFS, a technique for
        high-performance file allocation on disks.  VIFS uses bitmaps  to
        represent  both  free  blocks on the disk and allocated blocks in
        each file.  Allocation bitmaps provide  a  very  fast  method  of
        finding  blocks  close  to  the  last  allocated block in a file.
        Fragments (partial blocks) are used to store  the  overflow  from
        the  last  file  block;  the minimum size of a fragment is chosen
        when the file system is initialized.  Conventional file  systems,
        such  as  the  Berkeley  Fast File System (FFS), can store a file
        containing 96KB of data without using indirect blocks and  around
        16 MB of data for each indirect block.  With the same block size,
        VIFS can store up to about 10 MB of data without  using  indirect
        blocks  and  up to 500 MB of data per indirect block.  The design
        of VIFS allows some previously synchronous  operations  to  occur
        asynchronously,  resulting in significant speed improvements over
        FFS.  VIFS provides multiple  read-ahead  to  maintain  its  high
        speed when several processes are competing for disk accesses.  We
        provide experimental measurements taken from an implementation of
        Viva  in  a  BSD  4.3 kernel.  The measurements show that VIFS is
        significantly faster than FFS for nearly all file  system  opera-
        tions.


-- 
--
|  	Eric H. Herrin II - {rutgers,uunet}!ukma!eric, eric@ms.uky.edu	     |
|			  University of Kentucky			     |
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