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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 | .\" | |
f8a246f4 | 5 | .\" @(#)tunefs.8 6.4 (Berkeley) %G% |
be81fe9d | 6 | .\" |
e0509f13 | 7 | .TH TUNEFS 8 "" |
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8 | .UC 5 |
9 | .SH NAME | |
10 | tunefs \- tune up an existing file system | |
11 | .SH SYNOPSIS | |
12 | .B /etc/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. | |
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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. | |
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74 | .SH "SEE ALSO" |
75 | fs(5), | |
76 | newfs(8), | |
77 | mkfs(8) | |
78 | .PP | |
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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. | |
2c6735dc | 83 | (reprinted in the System Manager's Manual, SMM:14) |
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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, | |
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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. | |
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91 | .PP |
92 | You can tune a file system, but you can't tune a fish. |