1.\"- 2.\" Copyright (c) 2010 Edward Tomasz Napierala 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.\" $FreeBSD$ 27.\" 28.Dd January 3, 2010 29.Dt GCACHE 8 30.Os 31.Sh NAME 32.Nm gcache 33.Nd "control utility for CACHE GEOM class" 34.Sh SYNOPSIS 35.Nm 36.Cm create 37.Op Fl v 38.Op Fl b Ar blocksize 39.Op Fl s Ar size 40.Ar name 41.Ar prov 42.Nm 43.Cm configure 44.Op Fl v 45.Op Fl b Ar blocksize 46.Op Fl s Ar size 47.Ar name 48.Nm 49.Cm destroy 50.Op Fl fv 51.Ar name 52.Nm 53.Cm label 54.Op Fl v 55.Op Fl b Ar blocksize 56.Op Fl s Ar size 57.Ar name 58.Ar prov 59.Nm 60.Cm stop 61.Op Fl fv 62.Ar name ... 63.Nm 64.Cm clear 65.Op Fl v 66.Ar prov ... 67.Nm 68.Cm dump 69.Ar prov ... 70.Nm 71.Cm list 72.Nm 73.Cm status 74.Op Fl s Ar name 75.Nm 76.Cm load 77.Op Fl v 78.Nm 79.Cm unload 80.Op Fl v 81.Sh DESCRIPTION 82The 83.Nm 84utility is used to control GEOM cache, which can 85speed up read performance by sending fixed size 86read requests to its consumer. It has been developed to address 87the problem of a horrible read performance of a 64k blocksize FS 88residing on a RAID3 array with 8 data components, where a single 89disk component would only get 8k read requests, thus effectively 90killing disk performance under high load. 91.Pp 92Caching can be configured using two different methods: 93.Dq manual 94or 95.Dq automatic . 96When using the 97.Dq manual 98method, no metadata are stored on the devices, so the cached 99device has to be configured by hand every time it is needed. 100The 101.Dq automatic 102method uses on-disk metadata to detect devices. 103Once devices are labeled, they will be automatically detected and 104configured. 105.Pp 106The first argument to 107.Nm 108indicates an action to be performed: 109.Bl -tag -width ".Cm destroy" 110.It Cm create 111Cache the given devices with specified 112.Ar name . 113This is the 114.Dq manual 115method. 116The kernel module 117.Pa geom_cache.ko 118will be loaded if it is not loaded already. 119.It Cm label 120Cache the given devices with the specified 121.Ar name . 122This is the 123.Dq automatic 124method, where metadata are stored in every device's last sector. 125The kernel module 126.Pa geom_cache.ko 127will be loaded if it is not loaded already. 128.It Cm stop 129Turn off existing cache device by its 130.Ar name . 131This command does not touch on-disk metadata! 132.It Cm destroy 133Same as 134.Cm stop . 135.It Cm clear 136Clear metadata on the given devices. 137.It Cm dump 138Dump metadata stored on the given devices. 139.It Cm list 140See 141.Xr geom 8 . 142.It Cm status 143See 144.Xr geom 8 . 145.It Cm load 146See 147.Xr geom 8 . 148.It Cm unload 149See 150.Xr geom 8 . 151.El 152.Pp 153Additional options: 154.Bl -tag -width indent 155.It Fl f 156Force the removal of the specified cache device. 157.It Fl v 158Be more verbose. 159.El 160.Sh SYSCTL VARIABLES 161The following 162.Xr sysctl 8 163variables can be used to control the behavior of the 164.Nm CACHE 165GEOM class. 166The default value is shown next to each variable. 167.Bl -tag -width indent 168.It Va kern.geom.cache.used_hi : No 20 169.It Va kern.geom.cache.used_lo : No 5 170.It Va kern.geom.cache.idletime : No 5 171.It Va kern.geom.cache.timeout : No 10 172.It Va kern.geom.cache.enable : No 1 173.It Va kern.geom.cache.debug : No 0 174Debug level of the 175.Nm CACHE 176GEOM class. 177This can be set to a number between 0 and 3 inclusive. 178If set to 0 minimal debug information is printed, and if set to 3 the 179maximum amount of debug information is printed. 180.El 181.Sh EXIT STATUS 182Exit status is 0 on success, and 1 if the command fails. 183.Sh SEE ALSO 184.Xr geom 4 , 185.Xr geom 8 186.Sh HISTORY 187The 188.Nm 189utility appeared in 190.Fx 7.0 . 191.Sh AUTHORS 192.An Ruslan Ermilov Aq Mt ru@FreeBSD.org 193