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| 32 | .\" @(#)tunefs.8 8.2 (Berkeley) 12/11/93 |
| 33 | .\" $FreeBSD: src/sbin/tunefs/tunefs.8,v 1.11.2.6 2003/01/23 11:14:02 maxim Exp $ |
| 34 | .\" $DragonFly: src/sbin/tunefs/tunefs.8,v 1.2 2003/06/17 04:27:34 dillon Exp $ |
| 35 | .\" |
| 36 | .Dd December 11, 1993 |
| 37 | .Dt TUNEFS 8 |
| 38 | .Os |
| 39 | .Sh NAME |
| 40 | .Nm tunefs |
| 41 | .Nd tune up an existing filesystem |
| 42 | .Sh SYNOPSIS |
| 43 | .Nm |
| 44 | .Op Fl A |
| 45 | .Op Fl a Ar maxcontig |
| 46 | .Op Fl d Ar rotdelay |
| 47 | .Op Fl e Ar maxbpg |
| 48 | .Op Fl f Ar avgfilesize |
| 49 | .Op Fl m Ar minfree |
| 50 | .Bk -words |
| 51 | .Op Fl n Ar enable | disable |
| 52 | .Op Fl o Ar space | time |
| 53 | .Op Fl p |
| 54 | .Op Fl s Ar avgfpdir |
| 55 | .Ek |
| 56 | .Op Ar special | Ar filesystem |
| 57 | .Sh DESCRIPTION |
| 58 | .Nm Tunefs |
| 59 | is designed to change the dynamic parameters of a filesystem |
| 60 | which affect the layout policies. |
| 61 | The parameters which are to be changed are indicated by the flags |
| 62 | given below: |
| 63 | .Bl -tag -width indent |
| 64 | .It Fl A |
| 65 | The filesystem has several backups of the super-block. Specifying |
| 66 | this option will cause all backups to be modified as well as the |
| 67 | primary super-block. This is potentially dangerous - use with caution. |
| 68 | .It Fl a Ar maxcontig |
| 69 | Specify the maximum number of contiguous blocks that will |
| 70 | be laid out before forcing a rotational delay (see |
| 71 | .Fl d |
| 72 | below). |
| 73 | The default value is one, since most device drivers require |
| 74 | an interrupt per disk transfer. |
| 75 | Device drivers that can chain several buffers together in a single |
| 76 | transfer should set this to the maximum chain length. |
| 77 | .It Fl d Ar rotdelay |
| 78 | Specify the expected time (in milliseconds) |
| 79 | to service a transfer completion |
| 80 | interrupt and initiate a new transfer on the same disk. |
| 81 | It is used to decide how much rotational spacing to place between |
| 82 | successive blocks in a file. |
| 83 | .It Fl e Ar maxbpg |
| 84 | Indicate the maximum number of blocks any single file can |
| 85 | allocate out of a cylinder group before it is forced to begin |
| 86 | allocating blocks from another cylinder group. |
| 87 | Typically this value is set to about one quarter of the total blocks |
| 88 | in a cylinder group. |
| 89 | The intent is to prevent any single file from using up all the |
| 90 | blocks in a single cylinder group, |
| 91 | thus degrading access times for all files subsequently allocated |
| 92 | in that cylinder group. |
| 93 | The effect of this limit is to cause big files to do long seeks |
| 94 | more frequently than if they were allowed to allocate all the blocks |
| 95 | in a cylinder group before seeking elsewhere. |
| 96 | For filesystems with exclusively large files, |
| 97 | this parameter should be set higher. |
| 98 | .It Fl f Ar avgfilezsize |
| 99 | Specify the expected average file size. |
| 100 | .It Fl m Ar minfree |
| 101 | Specify the percentage of space held back |
| 102 | from normal users; the minimum free space threshold. |
| 103 | The default value used is 8%. |
| 104 | This value can be set to zero, however up to a factor of three |
| 105 | in throughput will be lost over the performance obtained at a 10% |
| 106 | threshold. |
| 107 | Settings of 5% and less force space optimization to |
| 108 | always be used which will greatly increase the overhead for file |
| 109 | writes. |
| 110 | Note that if the value is raised above the current usage level, |
| 111 | users will be unable to allocate files until enough files have |
| 112 | been deleted to get under the higher threshold. |
| 113 | .It Fl n Ar enable | disable |
| 114 | Turn on/off soft updates. |
| 115 | .It Fl o Ar space | time |
| 116 | The filesystem can either try to minimize the time spent |
| 117 | allocating blocks, or it can attempt to minimize the space |
| 118 | fragmentation on the disk. |
| 119 | Optimization for space has much |
| 120 | higher overhead for file writes. |
| 121 | The kernel normally changes the preference automatically as |
| 122 | the percent fragmentation changes on the filesystem. |
| 123 | .It Fl p |
| 124 | Show a summary of what the current tunable settings |
| 125 | are on the selected filesystem. More detailed information can be |
| 126 | obtained in the |
| 127 | .Xr dumpfs 8 |
| 128 | manual page. |
| 129 | .It Fl s Ar avgfpdir |
| 130 | Specify the expected number of files per directory. |
| 131 | .El |
| 132 | .Sh FILES |
| 133 | .Bl -tag -width /etc/fstab -compact |
| 134 | .It Pa /etc/fstab |
| 135 | read this to determine the device file for a |
| 136 | specified mount point. |
| 137 | .El |
| 138 | .Sh SEE ALSO |
| 139 | .Xr fs 5 , |
| 140 | .Xr dumpfs 8 , |
| 141 | .Xr newfs 8 |
| 142 | .Rs |
| 143 | .%A M. McKusick |
| 144 | .%A W. Joy |
| 145 | .%A S. Leffler |
| 146 | .%A R. Fabry |
| 147 | .%T "A Fast File System for UNIX" |
| 148 | .%J "ACM Transactions on Computer Systems 2" |
| 149 | .%N 3 |
| 150 | .%P pp 181-197 |
| 151 | .%D August 1984 |
| 152 | .%O "(reprinted in the BSD System Manager's Manual, SMM:5)" |
| 153 | .Re |
| 154 | .Sh BUGS |
| 155 | This program should work on mounted and active filesystems. |
| 156 | Because the super-block is not kept in the buffer cache, |
| 157 | the changes will only take effect if the program |
| 158 | is run on dismounted filesystems. |
| 159 | To change the root filesystem, the system must be rebooted |
| 160 | after the filesystem is tuned. |
| 161 | .\" Take this out and a Unix Demon will dog your steps from now until |
| 162 | .\" the time_t's wrap around. |
| 163 | .Pp |
| 164 | You can tune a filesystem, but you can't tune a fish. |
| 165 | .Sh HISTORY |
| 166 | The |
| 167 | .Nm |
| 168 | command appeared in |
| 169 | .Bx 4.2 . |