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Annotation of 43BSDReno/sbin/tunefs/tunefs.8, revision 1.1.1.1

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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