/share/doc/smm/05.fastfs/1.t
https://bitbucket.org/freebsd/freebsd-head/ · Raku · 112 lines · 112 code · 0 blank · 0 comment · 8 complexity · 344396509df0a4ea440c854e50ff68fe MD5 · raw file
- .\" Copyright (c) 1986, 1993
- .\" The Regents of the University of California. All rights reserved.
- .\"
- .\" Redistribution and use in source and binary forms, with or without
- .\" modification, are permitted provided that the following conditions
- .\" are met:
- .\" 1. Redistributions of source code must retain the above copyright
- .\" notice, this list of conditions and the following disclaimer.
- .\" 2. Redistributions in binary form must reproduce the above copyright
- .\" notice, this list of conditions and the following disclaimer in the
- .\" documentation and/or other materials provided with the distribution.
- .\" 3. All advertising materials mentioning features or use of this software
- .\" must display the following acknowledgement:
- .\" This product includes software developed by the University of
- .\" California, Berkeley and its contributors.
- .\" 4. Neither the name of the University nor the names of its contributors
- .\" may be used to endorse or promote products derived from this software
- .\" without specific prior written permission.
- .\"
- .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
- .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
- .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- .\" SUCH DAMAGE.
- .\"
- .\" @(#)1.t 8.1 (Berkeley) 6/8/93
- .\"
- .ds RH Introduction
- .NH
- Introduction
- .PP
- This paper describes the changes from the original 512 byte UNIX file
- system to the new one released with the 4.2 Berkeley Software Distribution.
- It presents the motivations for the changes,
- the methods used to effect these changes,
- the rationale behind the design decisions,
- and a description of the new implementation.
- This discussion is followed by a summary of
- the results that have been obtained,
- directions for future work,
- and the additions and changes
- that have been made to the facilities that are
- available to programmers.
- .PP
- The original UNIX system that runs on the PDP-11\(dg
- .FS
- \(dg DEC, PDP, VAX, MASSBUS, and UNIBUS are
- trademarks of Digital Equipment Corporation.
- .FE
- has simple and elegant file system facilities. File system input/output
- is buffered by the kernel;
- there are no alignment constraints on
- data transfers and all operations are made to appear synchronous.
- All transfers to the disk are in 512 byte blocks, which can be placed
- arbitrarily within the data area of the file system. Virtually
- no constraints other than available disk space are placed on file growth
- [Ritchie74], [Thompson78].*
- .FS
- * In practice, a file's size is constrained to be less than about
- one gigabyte.
- .FE
- .PP
- When used on the VAX-11 together with other UNIX enhancements,
- the original 512 byte UNIX file
- system is incapable of providing the data throughput rates
- that many applications require.
- For example,
- applications
- such as VLSI design and image processing
- do a small amount of processing
- on a large quantities of data and
- need to have a high throughput from the file system.
- High throughput rates are also needed by programs
- that map files from the file system into large virtual
- address spaces.
- Paging data in and out of the file system is likely
- to occur frequently [Ferrin82b].
- This requires a file system providing
- higher bandwidth than the original 512 byte UNIX
- one that provides only about
- two percent of the maximum disk bandwidth or about
- 20 kilobytes per second per arm [White80], [Smith81b].
- .PP
- Modifications have been made to the UNIX file system to improve
- its performance.
- Since the UNIX file system interface
- is well understood and not inherently slow,
- this development retained the abstraction and simply changed
- the underlying implementation to increase its throughput.
- Consequently, users of the system have not been faced with
- massive software conversion.
- .PP
- Problems with file system performance have been dealt with
- extensively in the literature; see [Smith81a] for a survey.
- Previous work to improve the UNIX file system performance has been
- done by [Ferrin82a].
- The UNIX operating system drew many of its ideas from Multics,
- a large, high performance operating system [Feiertag71].
- Other work includes Hydra [Almes78],
- Spice [Thompson80],
- and a file system for a LISP environment [Symbolics81].
- A good introduction to the physical latencies of disks is
- described in [Pechura83].
- .ds RH Old file system
- .sp 2
- .ne 1i