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				.\"-
				.\" Copyright (c) 2010 Edward Tomasz Napierala
				.\" All rights reserved.
				.\"
				.\" Redistribution and use in source and binary forms, with or without
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				.\" 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
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				.\"
				.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
				.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
				.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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				.\" $FreeBSD$
				.\"
				.Dd January 3, 2010
				.Dt GCACHE 8
				.Os
				.Sh NAME
				.Nm gcache
				.Nd "control utility for CACHE GEOM class"
				.Sh SYNOPSIS
				.Nm
				.Cm create
				.Op Fl v
				.Op Fl b Ar blocksize
				.Op Fl s Ar size
				.Ar name
				.Ar prov
				.Nm
				.Cm configure
				.Op Fl v
				.Op Fl b Ar blocksize
				.Op Fl s Ar size
				.Ar name
				.Nm
				.Cm destroy
				.Op Fl fv
				.Ar name
				.Nm
				.Cm label
				.Op Fl v
				.Op Fl b Ar blocksize
				.Op Fl s Ar size
				.Ar name
				.Ar prov
				.Nm
				.Cm stop
				.Op Fl fv
				.Ar name ...
				.Nm
				.Cm clear
				.Op Fl v
				.Ar prov ...
				.Nm
				.Cm dump
				.Ar prov ...
				.Nm
				.Cm list
				.Nm
				.Cm status
				.Op Fl s Ar name
				.Nm
				.Cm load
				.Op Fl v
				.Nm
				.Cm unload
				.Op Fl v
				.Sh DESCRIPTION
				The
				.Nm
				utility is used to control GEOM cache, which can
				speed up read performance by sending fixed size
				read requests to its consumer. It has been developed to address
				the problem of a horrible read performance of a 64k blocksize FS
				residing on a RAID3 array with 8 data components, where a single
				disk component would only get 8k read requests, thus effectively
				killing disk performance under high load.
				.Pp
				Caching can be configured using two different methods:
				.Dq manual
				or
				.Dq automatic .
				When using the
				.Dq manual
				method, no metadata are stored on the devices, so the cached
				device has to be configured by hand every time it is needed.
				The
				.Dq automatic
				method uses on-disk metadata to detect devices.
				Once devices are labeled, they will be automatically detected and
				configured.
				.Pp
				The first argument to
				.Nm
				indicates an action to be performed:
				.Bl -tag -width ".Cm destroy"
				.It Cm create
				Cache the given devices with specified
				.Ar name .
				This is the
				.Dq manual
				method.
				The kernel module
				.Pa geom_cache.ko
				will be loaded if it is not loaded already.
				.It Cm label
				Cache the given devices with the specified
				.Ar name .
				This is the
				.Dq automatic
				method, where metadata are stored in every device's last sector.
				The kernel module
				.Pa geom_cache.ko
				will be loaded if it is not loaded already.
				.It Cm stop
				Turn off existing cache device by its
				.Ar name .
				This command does not touch on-disk metadata!
				.It Cm destroy
				Same as
				.Cm stop .
				.It Cm clear
				Clear metadata on the given devices.
				.It Cm dump
				Dump metadata stored on the given devices.
				.It Cm list
				See
				.Xr geom 8 .
				.It Cm status
				See
				.Xr geom 8 .
				.It Cm load
				See
				.Xr geom 8 .
				.It Cm unload
				See
				.Xr geom 8 .
				.El
				.Pp
				Additional options:
				.Bl -tag -width indent
				.It Fl f
				Force the removal of the specified cache device.
				.It Fl v
				Be more verbose.
				.El
				.Sh SYSCTL VARIABLES
				The following
				.Xr sysctl 8
				variables can be used to control the behavior of the
				.Nm CACHE
				GEOM class.
				The default value is shown next to each variable.
				.Bl -tag -width indent
				.It Va kern.geom.cache.used_hi : No 20
				.It Va kern.geom.cache.used_lo : No 5
				.It Va kern.geom.cache.idletime : No 5
				.It Va kern.geom.cache.timeout : No 10
				.It Va kern.geom.cache.enable : No 1
				.It Va kern.geom.cache.debug : No 0
				Debug level of the
				.Nm CACHE
				GEOM class.
				This can be set to a number between 0 and 3 inclusive.
				If set to 0 minimal debug information is printed, and if set to 3 the
				maximum amount of debug information is printed.
				.El
				.Sh EXIT STATUS
				Exit status is 0 on success, and 1 if the command fails.
				.Sh SEE ALSO
				.Xr geom 4 ,
				.Xr geom 8
				.Sh HISTORY
				The
				.Nm
				utility appeared in
				.Fx 7.0 .
				.Sh AUTHORS
				.An Ruslan Ermilov Aq Mt ru@FreeBSD.org