29d0d30996
16384/2048. Following recent discussions on the -arch mailing list, involving dillon and mckusick, this change parallels the one made over a decade ago when the default was bumped up from 4096/512. This should provide significant performance improvements for most folks, less significant performance losses for a few folks and wasted space lost to large fragments for many folks. For discussion, please see the following thread in the -arch archive: Subject: Using a larger block size on large filesystems The discussion ceases to be relevant when the issue of partitioning schemes is raised.
316 lines
11 KiB
Groff
316 lines
11 KiB
Groff
.\" Copyright (c) 1983, 1987, 1991, 1993, 1994
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)newfs.8 8.6 (Berkeley) 5/3/95
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.\" $FreeBSD$
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.\"
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.Dd May 29, 2001
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.Dt NEWFS 8
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.Os
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.Sh NAME
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.Nm newfs ,
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.Nd construct a new file system
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.Sh SYNOPSIS
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.Nm
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.Op Fl NOU
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.Op Fl S Ar sector-size
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.Op Fl T Ar disktype
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.Op Fl a Ar maxcontig
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.Op Fl b Ar block-size
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.Op Fl c Ar cylinders
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.Op Fl d Ar rotdelay
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.Op Fl e Ar maxbpg
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.Op Fl f Ar frag-size
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.Op Fl g Ar avgfilesize
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.Op Fl h Ar avfpdir
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.Op Fl i Ar bytes
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.Op Fl k Ar skew
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.Op Fl l Ar interleave
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.Op Fl m Ar free space
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.Op Fl n Ar rotational positions
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.Op Fl o Ar optimization
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.Op Fl p Ar sectors
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.Op Fl r Ar revolutions
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.Op Fl s Ar size
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.Op Fl t Ar tracks
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.Op Fl u Ar sectors
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.Op Fl v
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.Op Fl x Ar sectors
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.Ar special
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.Sh DESCRIPTION
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.Nm Newfs
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is used to initialize and clear filesystems before first use.
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Before running
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.Nm
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the disk must be labeled using
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.Xr disklabel 8 .
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.Nm Newfs
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builds a file system on the specified special file.
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(We often refer to the
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.Dq special file
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as the
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.Dq disk ,
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although the special file need not be a physical disk.
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In fact, it need not even be special.)
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Typically the defaults are reasonable, however
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.Nm
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has numerous options to allow the defaults to be selectively overridden.
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.Pp
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The following options define the general layout policies:
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.Bl -tag -width indent
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.It Fl T Ar disktype
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For backward compatibility.
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.It Fl N
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Cause the file system parameters to be printed out
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without really creating the file system.
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.It Fl O
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Create a
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.Bx 4.3
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format filesystem.
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This options is primarily used to build root filesystems
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that can be understood by older boot ROMs.
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.It Fl U
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Enables soft updates on the new filesystem.
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.It Fl a Ar maxcontig
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Specify the maximum number of contiguous blocks that will be
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laid out before forcing a rotational delay (see the
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.Fl d
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option).
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The default value is 1.
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See
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.Xr tunefs 8
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for more details on how to set this option.
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.It Fl b Ar block-size
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The block size of the file system, in bytes. It must be a power of 2. The
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default size is 16384 bytes, and the smallest allowable size is 4096 bytes.
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The optimal block:fragment ratio is 8:1.
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Other ratios are possible, but are not recommended,
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and may produce unpredictable results.
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.It Fl c Ar #cylinders/group
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The number of cylinders per cylinder group in a file system. The default
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is to compute the maximum allowed by the other parameters. This value is
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dependent on a number of other parameters, in particular the block size
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and the number of bytes per inode.
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.It Fl d Ar rotdelay
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This parameter once specified the minimum time in milliseconds required to
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initiate another disk transfer on the same cylinder. It was used in determining
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the rotationally optimal layout for disk blocks within a file. Modern disks
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with read/write-behind achieve higher performance with this feature disabled, so
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this value should be left at the default value of 0 milliseconds. See
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.Xr tunefs 8
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for more details on how to set this option.
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.It Fl e Ar maxbpg
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Indicate the maximum number of blocks any single file can
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allocate out of a cylinder group before it is forced to begin
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allocating blocks from another cylinder group.
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The default is about one quarter of the total blocks in a cylinder group.
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See
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.Xr tunefs 8
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for more details on how to set this option.
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.It Fl f Ar frag-size
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The fragment size of the file system in bytes. It must be a power of two
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ranging in value between
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.Ar blocksize Ns /8
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and
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.Ar blocksize .
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The default is 2048 bytes.
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.It Fl g Ar avgfilesize
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The expected average file size for the file system.
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.It Fl h Ar avgfpdir
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The expected average number of files per directory on the file system.
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.It Fl i Ar number of bytes per inode
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Specify the density of inodes in the file system.
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The default is to create an inode for every
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.Pq 4 * Ar frag-size
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bytes of data space.
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If fewer inodes are desired, a larger number should be used;
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to create more inodes a smaller number should be given.
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One inode is required for each distinct file, so this value effectively
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specifies the average file size on the file system.
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.It Fl m Ar free space \&%
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The percentage of space reserved from normal users; the minimum free
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space threshold.
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The default value used is
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defined by
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.Dv MINFREE
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from
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.Aq Pa ufs/ffs/fs.h ,
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currently 8%.
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See
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.Xr tunefs 8
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for more details on how to set this option.
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.It Fl n Ar number of distinguished rotational positions
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UFS has the ability to keep track of the availability of blocks at different
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rotational positions, so that it could lay out the data to be picked up with
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minimum rotational latency. This parameter specifies the default number of
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rotational positions to distinguish.
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.Pp
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Nowadays this value should be set to 1 (which essentially disables the
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rotational position table) because modern drives with read-ahead and
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write-behind do better without the rotational position table.
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.It Fl o Ar optimization\ preference
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.Pq Ar space No or Ar time .
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The file system can either be instructed to try to minimize the time spent
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allocating blocks, or to try to minimize the space fragmentation on the disk.
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If the value of minfree (see above) is less than 8%,
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the default is to optimize for
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.Ar space ;
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if the value of minfree is greater than or equal to 8%,
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the default is to optimize for
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.Ar time .
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See
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.Xr tunefs 8
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for more details on how to set this option.
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.It Fl s Ar size
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The size of the file system in sectors. This value defaults to the size of the
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raw partition specified in
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.Ar special
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(in other words,
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.Nm
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will use the entire partition for the file system).
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.It Fl v
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Specify that the disk does not contain any partitions, and that
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.Nm
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should build a file system on the whole disk.
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This option is useful for synthetic disks such as
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.Nm vinum .
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.El
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.Pp
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The following options override the standard sizes for the disk geometry.
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Their default values are taken from the disk label.
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Changing these defaults is useful only when using
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.Nm
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to build a file system whose raw image will eventually be used on a
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different type of disk than the one on which it is initially created
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(for example on a write-once disk).
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Note that changing any of these values from their defaults will make
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it impossible for
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.Xr fsck 8
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to find the alternate superblocks if the standard superblock is lost.
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.Bl -tag -width indent
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.It Fl S Ar sector-size
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The size of a sector in bytes (almost never anything but 512).
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.It Fl k Ar sector \&0 skew , per track
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Used to describe perturbations in the media format to compensate for
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a slow controller.
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Track skew is the offset of sector 0 on track N relative to sector 0
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on track N-1 on the same cylinder.
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This option is of historical importance only; modern controllers are always fast
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enough to handle operations back-to-back.
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.It Fl l Ar hardware sector interleave
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Used to describe perturbations in the media format to compensate for
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a slow controller.
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Interleave is physical sector interleave on each track,
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specified as the denominator of the ratio:
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.Dl sectors read/sectors passed over
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Thus an interleave of 1/1 implies contiguous layout, while 1/2 implies
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logical sector 0 is separated by one sector from logical sector 1.
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This option is of historical importance only; the physical sector layout of
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modern disks is not visible from outside.
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.It Fl p Ar spare sectors per track
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Spare sectors (bad sector replacements) are physical sectors that occupy
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space at the end of each track.
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They are not counted as part of the sectors/track
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.Pq Fl u
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since they are not available to the file system for data allocation.
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This option is of historical importance only. Modern disks perform their own
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bad sector allocation.
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.It Fl r Ar revolutions/minute
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The speed of the disk in revolutions per minute. This value is no longer of
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interest, since all the parameters which depend on it are usually disabled.
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.It Fl t Ar #tracks/cylinder
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The number of tracks/cylinder available for data allocation by the file
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system.
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The default is 1.
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If zero is specified, the value from the disklabel will be used.
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.It Fl u Ar sectors/track
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The number of sectors per track available for data allocation by the file
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system.
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The default is 4096.
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If zero is specified, the value from the disklabel will be used.
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This does not include sectors reserved at the end of each track for bad
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block replacement (see the
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.Fl p
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option).
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.It Fl x Ar spare sectors per cylinder
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Spare sectors (bad sector replacements) are physical sectors that occupy
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space at the end of the last track in the cylinder.
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They are deducted from the sectors/track
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.Pq Fl u
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of the last track of each cylinder since they are not available to the file
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system for data allocation.
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This option is of historical importance only. Modern disks perform their own
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bad sector allocation.
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.El
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.Sh EXAMPLES
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.Dl newfs /dev/ad3s1a
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.Pp
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Creates a new ufs file system on
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.Pa ad3s1a .
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.Nm
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will use a block size of 16384 bytes, a fragment size of 2048 bytes
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and the largest possible number of cylinders per group.
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These values tend to produce better performance for most applications
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than the historical defaults
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(8192 byte block size and 1024 byte fragment size).
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This large fragment size
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may lead to large amounts of wasted space
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on filesystems that contain a large number of small files.
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.Sh SEE ALSO
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.Xr fdformat 1 ,
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.Xr disktab 5 ,
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.Xr fs 5 ,
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.Xr camcontrol 8 ,
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.Xr disklabel 8 ,
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.Xr diskpart 8 ,
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.Xr dumpfs 8 ,
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.Xr fsck 8 ,
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.Xr mount 8 ,
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.Xr tunefs 8 ,
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.Xr vinum 8
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.Rs
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.%A M. McKusick
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.%A W. Joy
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.%A S. Leffler
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.%A R. Fabry
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.%T A Fast File System for UNIX
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.%J ACM Transactions on Computer Systems 2
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.%V 3
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.%P pp 181-197
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.%D August 1984
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.%O (reprinted in the BSD System Manager's Manual)
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.Re
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.Sh HISTORY
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The
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.Nm
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command appeared in
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.Bx 4.2 .
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