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Annotation of 43BSDReno/sbin/tunefs/tunefs.8, revision 1.1

1.1     ! root        1: .\" Copyright (c) 1983 Regents of the University of California.
        !             2: .\" All rights reserved.  The Berkeley software License Agreement
        !             3: .\" specifies the terms and conditions for redistribution.
        !             4: .\"
        !             5: .\"    @(#)tunefs.8    6.5 (Berkeley) 6/24/90
        !             6: .\"
        !             7: .TH TUNEFS 8 "June 24, 1990"
        !             8: .UC 5
        !             9: .SH NAME
        !            10: tunefs \- tune up an existing file system
        !            11: .SH SYNOPSIS
        !            12: .B tunefs
        !            13: .I tuneup-options
        !            14: .IR special | filesys
        !            15: .SH DESCRIPTION
        !            16: .I Tunefs
        !            17: is designed to change the dynamic parameters of a file system
        !            18: which affect the layout policies.
        !            19: The parameters which are to be changed are indicated by the flags
        !            20: given below:
        !            21: .IP "\fB\-a\fP maxcontig"
        !            22: .br
        !            23: This specifies the maximum number of contiguous blocks that will
        !            24: be laid out before forcing a rotational delay (see \-d below).
        !            25: The default value is one, since most device drivers require
        !            26: an interrupt per disk transfer.
        !            27: Device drivers that can chain several buffers together in a single
        !            28: transfer should set this to the maximum chain length.
        !            29: .IP "\fB\-d\fP rotdelay"
        !            30: .br
        !            31: This specifies the expected time (in milliseconds)
        !            32: to service a transfer completion
        !            33: interrupt and initiate a new transfer on the same disk.
        !            34: It is used to decide how much rotational spacing to place between
        !            35: successive blocks in a file.
        !            36: .IP "\fB\-e\fP maxbpg"
        !            37: .br
        !            38: This indicates the maximum number of blocks any single file can
        !            39: allocate out of a cylinder group before it is forced to begin
        !            40: allocating blocks from another cylinder group.
        !            41: Typically this value is set to about one quarter of the total blocks
        !            42: in a cylinder group.
        !            43: The intent is to prevent any single file from using up all the
        !            44: blocks in a single cylinder group,
        !            45: thus degrading access times for all files subsequently allocated 
        !            46: in that cylinder group.
        !            47: The effect of this limit is to cause big files to do long seeks
        !            48: more frequently than if they were allowed to allocate all the blocks
        !            49: in a cylinder group before seeking elsewhere.
        !            50: For file systems with exclusively large files, 
        !            51: this parameter should be set higher.
        !            52: .IP "\fB\-m\fP minfree"
        !            53: .br
        !            54: This value specifies the percentage of space held back
        !            55: from normal users; the minimum free space threshold.
        !            56: The default value used is 10%.
        !            57: This value can be set to zero, however up to a factor of three
        !            58: in throughput will be lost over the performance obtained at a 10%
        !            59: threshold.
        !            60: Note that if the value is raised above the current usage level,
        !            61: users will be unable to allocate files until enough files have
        !            62: been deleted to get under the higher threshold.
        !            63: .IP "\fB\-o\fP optimization preference"
        !            64: .br
        !            65: The file system can either try to minimize the time spent
        !            66: allocating blocks, or it can attempt minimize the space
        !            67: fragmentation on the disk.
        !            68: If the value of minfree (see above) is less than 10%,
        !            69: then the file system should optimize for space to avoid
        !            70: running out of full sized blocks.
        !            71: For values of minfree greater than or equal to 10%,
        !            72: fragmentation is unlikely to be problematical, and
        !            73: the file system can be optimized for time.
        !            74: .SH "SEE ALSO"
        !            75: fs(5),
        !            76: newfs(8),
        !            77: mkfs(8)
        !            78: .PP
        !            79: M. McKusick, W. Joy, S. Leffler, R. Fabry,
        !            80: ``A Fast File System for UNIX'',
        !            81: \fIACM Transactions on Computer Systems 2\fP, 3.
        !            82: pp 181-197, August 1984.
        !            83: (reprinted in the System Manager's Manual, SMM:14)
        !            84: .SH BUGS
        !            85: This program should work on mounted and active file systems.
        !            86: Because the super-block is not kept in the buffer cache,
        !            87: the changes will only take effect if the program
        !            88: is run on dismounted file systems.
        !            89: To change the root file system, the system must be rebooted
        !            90: after the file system is tuned.
        !            91: .PP
        !            92: You can tune a file system, but you can't tune a fish.

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