1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
|
.\" $NetBSD: tunefs.8,v 1.8 1995/03/18 15:01:29 cgd Exp $
.\"
.\" Copyright (c) 1983, 1991, 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.
.\"
.\" @(#)tunefs.8 8.2 (Berkeley) 12/11/93
.\"
.Dd December 11, 1993
.Dt TUNEFS 8
.Os BSD 4.2
.Sh NAME
.Nm tunefs
.Nd tune up an existing file system
.Sh SYNOPSIS
.Nm tunefs
.Op Fl a Ar maxcontig
.Op Fl d Ar rotdelay
.Op Fl e Ar maxbpg
.Op Fl m Ar minfree
.Bk -words
.Op Fl o Ar optimize_preference
.Ek
.Op Ar special | Ar filesys
.Sh DESCRIPTION
.Nm Tunefs
is designed to change the dynamic parameters of a file system
which affect the layout policies.
The parameters which are to be changed are indicated by the flags
given below:
.Bl -tag -width Ds
.It Fl a Ar maxcontig
This specifies the maximum number of contiguous blocks that will
be laid out before forcing a rotational delay (see
.Fl d
below).
The default value is one, since most device drivers require
an interrupt per disk transfer.
Device drivers that can chain several buffers together in a single
transfer should set this to the maximum chain length.
.It Fl d Ar rotdelay
This specifies the expected time (in milliseconds)
to service a transfer completion
interrupt and initiate a new transfer on the same disk.
It is used to decide how much rotational spacing to place between
successive blocks in a file.
.It Fl e Ar maxbpg
This indicates the maximum number of blocks any single file can
allocate out of a cylinder group before it is forced to begin
allocating blocks from another cylinder group.
Typically this value is set to about one quarter of the total blocks
in a cylinder group.
The intent is to prevent any single file from using up all the
blocks in a single cylinder group,
thus degrading access times for all files subsequently allocated
in that cylinder group.
The effect of this limit is to cause big files to do long seeks
more frequently than if they were allowed to allocate all the blocks
in a cylinder group before seeking elsewhere.
For file systems with exclusively large files,
this parameter should be set higher.
.It Fl m Ar minfree
This value specifies the percentage of space held back
from normal users; the minimum free space threshold.
The default value used is 10%.
This value can be set to zero, however up to a factor of three
in throughput will be lost over the performance obtained at a 10%
threshold.
Note that if the value is raised above the current usage level,
users will be unable to allocate files until enough files have
been deleted to get under the higher threshold.
.It Fl o Ar optimize_preference
The file system can either try to minimize the time spent
allocating blocks, or it can attempt to minimize the space
fragmentation on the disk.
If the value of minfree (see above) is less than 10%,
then the file system should optimize for space to avoid
running out of full sized blocks.
For values of minfree greater than or equal to 10%,
fragmentation is unlikely to be problematical, and
the file system can be optimized for time.
.El
.Sh SEE ALSO
.Xr fs 5 ,
.Xr dumpfs 8 ,
.Xr newfs 8 ,
.Xr mkfs 8
.Rs
.%A M. McKusick
.%A W. Joy
.%A S. Leffler
.%A R. Fabry
.%T "A Fast File System for UNIX"
.%J "ACM Transactions on Computer Systems 2"
.%N 3
.%P pp 181-197
.%D August 1984
.%O "(reprinted in the BSD System Manager's Manual, SMM:5)"
.Re
.Sh BUGS
This program should work on mounted and active file systems.
Because the super-block is not kept in the buffer cache,
the changes will only take effect if the program
is run on dismounted file systems.
To change the root file system, the system must be rebooted
after the file system is tuned.
.Pp
You can tune a file system, but you can't tune a fish.
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.2 .
|
