193 lines
4.5 KiB
Groff
193 lines
4.5 KiB
Groff
.\"-
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.\" Copyright (c) 2010 Edward Tomasz Napierala
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.\" 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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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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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.\" $FreeBSD$
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.\"
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.Dd January 3, 2010
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.Dt GCACHE 8
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.Os
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.Sh NAME
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.Nm gcache
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.Nd "control utility for CACHE GEOM class"
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.Sh SYNOPSIS
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.Nm
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.Cm create
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.Op Fl v
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.Op Fl b Ar blocksize
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.Op Fl s Ar size
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.Ar name
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.Ar prov
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.Nm
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.Cm configure
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.Op Fl v
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.Op Fl b Ar blocksize
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.Op Fl s Ar size
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.Ar name
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.Nm
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.Cm destroy
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.Op Fl fv
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.Ar name
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.Nm
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.Cm label
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.Op Fl v
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.Op Fl b Ar blocksize
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.Op Fl s Ar size
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.Ar name
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.Ar prov
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.Nm
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.Cm stop
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.Op Fl fv
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.Ar name ...
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.Nm
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.Cm clear
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.Op Fl v
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.Ar prov ...
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.Nm
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.Cm dump
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.Ar prov ...
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.Nm
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.Cm list
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.Nm
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.Cm status
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.Op Fl s Ar name
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.Nm
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.Cm load
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.Op Fl v
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.Nm
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.Cm unload
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.Op Fl v
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.Sh DESCRIPTION
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The
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.Nm
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utility is used to control GEOM cache, which can
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speed up read performance by sending fixed size
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read requests to its consumer. It has been developed to address
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the problem of a horrible read performance of a 64k blocksize FS
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residing on a RAID3 array with 8 data components, where a single
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disk component would only get 8k read requests, thus effectively
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killing disk performance under high load.
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.Pp
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Caching can be configured using two different methods:
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.Dq manual
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or
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.Dq automatic .
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When using the
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.Dq manual
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method, no metadata are stored on the devices, so the cached
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device has to be configured by hand every time it is needed.
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The
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.Dq automatic
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method uses on-disk metadata to detect devices.
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Once devices are labeled, they will be automatically detected and
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configured.
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.Pp
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The first argument to
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.Nm
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indicates an action to be performed:
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.Bl -tag -width ".Cm destroy"
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.It Cm create
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Cache the given devices with specified
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.Ar name .
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This is the
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.Dq manual
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method.
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The kernel module
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.Pa geom_cache.ko
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will be loaded if it is not loaded already.
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.It Cm label
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Cache the given devices with the specified
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.Ar name .
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This is the
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.Dq automatic
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method, where metadata are stored in every device's last sector.
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The kernel module
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.Pa geom_cache.ko
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will be loaded if it is not loaded already.
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.It Cm stop
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Turn off existing cache device by its
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.Ar name .
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This command does not touch on-disk metadata!
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.It Cm destroy
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Same as
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.Cm stop .
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.It Cm clear
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Clear metadata on the given devices.
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.It Cm dump
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Dump metadata stored on the given devices.
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.It Cm list
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See
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.Xr geom 8 .
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.It Cm status
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See
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.Xr geom 8 .
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.It Cm load
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See
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.Xr geom 8 .
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.It Cm unload
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See
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.Xr geom 8 .
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.El
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.Pp
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Additional options:
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.Bl -tag -width indent
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.It Fl f
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Force the removal of the specified cache device.
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.It Fl v
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Be more verbose.
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.El
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.Sh SYSCTL VARIABLES
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The following
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.Xr sysctl 8
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variables can be used to control the behavior of the
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.Nm CACHE
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GEOM class.
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The default value is shown next to each variable.
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.Bl -tag -width indent
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.It Va kern.geom.cache.used_hi : No 20
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.It Va kern.geom.cache.used_lo : No 5
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.It Va kern.geom.cache.idletime : No 5
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.It Va kern.geom.cache.timeout : No 10
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.It Va kern.geom.cache.enable : No 1
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.It Va kern.geom.cache.debug : No 0
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Debug level of the
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.Nm CACHE
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GEOM class.
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This can be set to a number between 0 and 3 inclusive.
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If set to 0 minimal debug information is printed, and if set to 3 the
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maximum amount of debug information is printed.
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.El
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.Sh EXIT STATUS
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Exit status is 0 on success, and 1 if the command fails.
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.Sh SEE ALSO
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.Xr geom 4 ,
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.Xr geom 8
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.Sh HISTORY
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The
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.Nm
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utility appeared in
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.Fx 7.0 .
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.Sh AUTHORS
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.An Ruslan Ermilov Aq Mt ru@FreeBSD.org
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