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.Dd January 3, 2010 27.Dt GCACHE 8 28.Os 29.Sh NAME 30.Nm gcache 31.Nd "control utility for CACHE GEOM class" 32.Sh SYNOPSIS 33.Nm 34.Cm create 35.Op Fl v 36.Op Fl b Ar blocksize 37.Op Fl s Ar size 38.Ar name 39.Ar prov 40.Nm 41.Cm configure 42.Op Fl v 43.Op Fl b Ar blocksize 44.Op Fl s Ar size 45.Ar name 46.Nm 47.Cm destroy 48.Op Fl fv 49.Ar name 50.Nm 51.Cm label 52.Op Fl v 53.Op Fl b Ar blocksize 54.Op Fl s Ar size 55.Ar name 56.Ar prov 57.Nm 58.Cm stop 59.Op Fl fv 60.Ar name ... 61.Nm 62.Cm clear 63.Op Fl v 64.Ar prov ... 65.Nm 66.Cm dump 67.Ar prov ... 68.Nm 69.Cm list 70.Nm 71.Cm status 72.Op Fl s Ar name 73.Nm 74.Cm load 75.Op Fl v 76.Nm 77.Cm unload 78.Op Fl v 79.Sh DESCRIPTION 80The 81.Nm 82utility is used to control GEOM cache, which can 83speed up read performance by sending fixed size 84read requests to its consumer. It has been developed to address 85the problem of a horrible read performance of a 64k blocksize FS 86residing on a RAID3 array with 8 data components, where a single 87disk component would only get 8k read requests, thus effectively 88killing disk performance under high load. 89.Pp 90Caching can be configured using two different methods: 91.Dq manual 92or 93.Dq automatic . 94When using the 95.Dq manual 96method, no metadata are stored on the devices, so the cached 97device has to be configured by hand every time it is needed. 98The 99.Dq automatic 100method uses on-disk metadata to detect devices. 101Once devices are labeled, they will be automatically detected and 102configured. 103.Pp 104The first argument to 105.Nm 106indicates an action to be performed: 107.Bl -tag -width ".Cm destroy" 108.It Cm create 109Cache the given devices with specified 110.Ar name . 111This is the 112.Dq manual 113method. 114The kernel module 115.Pa geom_cache.ko 116will be loaded if it is not loaded already. 117.It Cm label 118Cache the given devices with the specified 119.Ar name . 120This is the 121.Dq automatic 122method, where metadata are stored in every device's last sector. 123The kernel module 124.Pa geom_cache.ko 125will be loaded if it is not loaded already. 126.It Cm stop 127Turn off existing cache device by its 128.Ar name . 129This command does not touch on-disk metadata! 130.It Cm destroy 131Same as 132.Cm stop . 133.It Cm clear 134Clear metadata on the given devices. 135.It Cm dump 136Dump metadata stored on the given devices. 137.It Cm list 138See 139.Xr geom 8 . 140.It Cm status 141See 142.Xr geom 8 . 143.It Cm load 144See 145.Xr geom 8 . 146.It Cm unload 147See 148.Xr geom 8 . 149.El 150.Pp 151Additional options: 152.Bl -tag -width indent 153.It Fl f 154Force the removal of the specified cache device. 155.It Fl v 156Be more verbose. 157.El 158.Sh SYSCTL VARIABLES 159The following 160.Xr sysctl 8 161variables can be used to control the behavior of the 162.Nm CACHE 163GEOM class. 164The default value is shown next to each variable. 165.Bl -tag -width indent 166.It Va kern.geom.cache.used_hi : No 20 167.It Va kern.geom.cache.used_lo : No 5 168.It Va kern.geom.cache.idletime : No 5 169.It Va kern.geom.cache.timeout : No 10 170.It Va kern.geom.cache.enable : No 1 171.It Va kern.geom.cache.debug : No 0 172Debug level of the 173.Nm CACHE 174GEOM class. 175This can be set to a number between 0 and 3 inclusive. 176If set to 0 minimal debug information is printed, and if set to 3 the 177maximum amount of debug information is printed. 178.El 179.Sh EXIT STATUS 180Exit status is 0 on success, and 1 if the command fails. 181.Sh SEE ALSO 182.Xr geom 4 , 183.Xr geom 8 184.Sh HISTORY 185The 186.Nm 187utility appeared in 188.Fx 7.0 . 189.Sh AUTHORS 190.An Ruslan Ermilov Aq Mt ru@FreeBSD.org 191