manual page first distributed with 4.2BSD

SCCS-vsn: sbin/tunefs/tunefs.8 5.1

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+.\" Copyright (c) 1983 Regents of the University of California.
+.\" All rights reserved.  The Berkeley software License Agreement
+.\" specifies the terms and conditions for redistribution.
+.\"
+.\"    @(#)tunefs.8    5.1 (Berkeley) %G%
+.\"
+.TH TUNEFS 8 "20 February 1983"
+.UC 5
+.SH NAME
+tunefs \- tune up an existing file system
+.SH SYNOPSIS
+.B /etc/tunefs
+.I tuneup-options
+.IR special | filesys
+.SH DESCRIPTION
+.I 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:
+.IP "\fB\-a\fP maxcontig"
+.br
+This specifies the maximum number of contiguous blocks that will
+be laid out before forcing a rotational delay (see \-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.
+.IP "\fB\-d\fP rotdelay"
+.br
+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.
+.IP "\fB\-e\fP maxbpg"
+.br
+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.
+.IP "\fB\-m\fP minfree"
+.br
+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.
+.SH "SEE ALSO"
+fs(5),
+newfs(8),
+mkfs(8)
+.PP
+McKusick, Joy, Leffler; "A Fast File System for Unix",
+Computer Systems Research Group, Dept of EECS, Berkeley, CA 94720;
+TR #7, September 1982.
+.SH BUGS
+This program should work on mounted and active file systems.
+Because the super-block is not kept in the buffer cache,
+the program will only take effect if it is run on dismounted file systems.
+(if run on the root file system, the system must be rebooted)
+.PP
+You can tune a file system, but you can't tune a fish.