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.\" $OpenBSD: ffs_softupdates.4,v 1.4 2000/04/30 18:41:30 millert Exp $
.\"
.\" Copyright (c) 1998 Todd C. Miller <Todd.Miller@courtesan.com>
.\" 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. The name of the author may not be used to endorse or promote products
.\" derived from this software without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED ``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 AUTHOR 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.
.\"
.Dd March 15, 1998
.Dt FFS_SOFTUPDATES 4
.Os
.Sh NAME
.Nm ffs_softupdates
.Nd asynchronous file system writes
.Sh DESCRIPTION
The
.Nm FFS_SOFTUPDATES
kernel config option enables a scheme that uses partial ordering of
buffer cache operations to allow metadata updates in the fast filesystem
to happen asynchronously, increasing write performance significantly.
Normally, the
.Em ffs
filesystem writes metadata updates synchronously which exacts
a performance penalty in favor of filesystem integrity.
With
.Em soft updates ,
you gain the performance of asynchronous writes while retaining the safety
of synchronous metadata updates.
.Pp
.Em Soft Updates
must be enabled on a per-filesystem basis. To do this, boot into
single user mode and run
.Dq tunefs -s enable special
on each character special disk device you want to enable
.Em soft updates
on, then run
.Dq reboot -n .
.Sh CAVEATS
Soft updates should be considered experimental at this time.
.Pp
CPUs with a small kernel address space, such as the sun4 and
sun4c, do not have enough kernel memory to support
.Em Soft Updates .
Attempts to use
.Em Soft Updates
on these CPUs will cause a kernel hang or panic after a short period of
use as the kernel will quickly run out of memory. This is not related
to the amount of physical memory present in the machine--it is a limitation
of the CPU architecture.
.Pp
There should be a
.Xr mount 2
option to enable
.Em soft updates .
.br
The current license for
.Nm
is more restrictive than the rest of the
.Ox
kernel; this will be changed at a future date.
.Sh AUTHOR
Marshall Kirk McKusick
.Sh LICENSE
The following are the copyrights and redistribution conditions that
apply to this copy of the soft update software. For a license
to use, redistribute or sell the soft update software under
conditions other than those described here, please contact the
author at one of the following addresses:
.Bd -literal -offset indent
Marshall Kirk McKusick mckusick@mckusick.com
1614 Oxford Street +1-510-843-9542
Berkeley, CA 94709-1608
USA
.Ed
.Pp
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
.Bl -tag -width XXX
.It 1.
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
.It 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.
.It 3.
None of the names of McKusick, Ganger, Patt, or the University of
Michigan may be used to endorse or promote products derived from
this software without specific prior written permission.
.It 4.
Redistributions in any form must be accompanied by information on
how to obtain complete source code for any accompanying software
that uses this software. This source code must either be included
in the distribution or be available for no more than the cost of
distribution plus a nominal fee, and must be freely redistributable
under reasonable conditions. For an executable file, complete
source code means the source code for all modules it contains.
It does not mean source code for modules or files that typically
accompany the operating system on which the executable file runs,
e.g., standard library modules or system header files.
.El
.Pp
THIS SOFTWARE IS PROVIDED BY MARSHALL KIRK MCKUSICK ``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 MARSHALL KIRK MCKUSICK 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.
.Sh SEE ALSO
.Xr fs 5 ,
.Xr config 8 ,
.Xr sysctl 8 ,
.Xr tunefs 8 .
.Rs
.%T "A Fast Filesystem for UNIX"
.%A Marshall Kirk McKusick
.%A William N. Joy
.%A Samuel J. Leffler
.%A Robert S. Fabry
.%C Computer Science Research Group
.Re
.Pp
.Rs
.%T "Soft Updates: A Solution to the Metadata Update Problem in File Systems"
.%A Gregory R. Ganger
.%A Yale N. Patt
.%R CSE-TR-254-95
.%C "University of Michigan, Ann Arbor"
.Re
.br
.Li http://www.ece.cmu.edu/~ganger/papers/CSE-TR-254-95/
|
