freebsd-dev/lib/geom/cache/gcache.8
Brooks Davis e4b0a90e77 Normalize the g(eom,cache,part,...) build.
Rather then combining hardlink creation for the geom(8) binary with
shared library build, move libraries to src/lib/geom so they are
built and installed normally.  Create a common Makefile.classes
which is included by both lib/geom/Makefile and sbin/geom/Makefile
so the symlink and libraries stay in sync.

The relocation of libraries allows libraries to be build for 32-bit
compat.  This also reduces the number of non-standard builds in
the system.

This commit is not sufficent to run a 32-bit /sbin/geom on a 64-bit
system out of the box as it will look in the wrong place for libraries
unless GEOM_LIBRARY_PATH is set appropriatly in the environment.

Reviewed by:	bdrewery
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D15360
2018-06-25 19:55:15 +00:00

193 lines
4.5 KiB
Groff

.\"-
.\" Copyright (c) 2010 Edward Tomasz Napierala
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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