gcache(8) [freebsd man page]
GCACHE(8) BSD System Manager's Manual GCACHE(8) NAME
gcache -- control utility for CACHE GEOM class SYNOPSIS
gcache create [-v] [-b blocksize] [-s size] name prov gcache configure [-v] [-b blocksize] [-s size] name gcache destroy [-fv] name gcache label [-v] [-b blocksize] [-s size] name prov gcache stop [-fv] name ... gcache clear [-v] prov ... gcache dump prov ... gcache list gcache status [-s name] gcache load [-v] gcache unload [-v] DESCRIPTION
The gcache 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 com- ponents, where a single disk component would only get 8k read requests, thus effectively killing disk performance under high load. Caching can be configured using two different methods: ``manual'' or ``automatic''. When using the ``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 ``automatic'' method uses on-disk metadata to detect devices. Once devices are labeled, they will be automatically detected and configured. The first argument to gcache indicates an action to be performed: create Cache the given devices with specified name. This is the ``manual'' method. The kernel module geom_cache.ko will be loaded if it is not loaded already. label Cache the given devices with the specified name. This is the ``automatic'' method, where metadata are stored in every device's last sector. The kernel module geom_cache.ko will be loaded if it is not loaded already. stop Turn off existing cache device by its name. This command does not touch on-disk metadata! destroy Same as stop. clear Clear metadata on the given devices. dump Dump metadata stored on the given devices. list See geom(8). status See geom(8). load See geom(8). unload See geom(8). Additional options: -f Force the removal of the specified cache device. -v Be more verbose. SYSCTL VARIABLES
The following sysctl(8) variables can be used to control the behavior of the CACHE GEOM class. The default value is shown next to each vari- able. kern.geom.cache.used_hi: 20 kern.geom.cache.used_lo: 5 kern.geom.cache.idletime: 5 kern.geom.cache.timeout: 10 kern.geom.cache.enable: 1 kern.geom.cache.debug: 0 Debug level of the 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. EXIT STATUS
Exit status is 0 on success, and 1 if the command fails. SEE ALSO
geom(4), geom(8) HISTORY
The gcache utility appeared in FreeBSD 7.0. AUTHORS
Ruslan Ermilov <ru@FreeBSD.org> BSD
January 3, 2010 BSD
Check Out this Related Man Page
GEOM(8) BSD System Manager's Manual GEOM(8) NAME
geom -- universal control utility for GEOM classes SYNOPSIS
geom class help geom class list [-a] [name ...] geom class status [-ags] [name ...] geom class load [-v] geom class unload [-v] DESCRIPTION
The geom utility is used to control various GEOM classes. A class has to be aware of geom(8) communication methods, but there are also some standard commands which can be used for existing geom(8) unaware classes. Here is the list of standard commands: help List all available commands for the given class. list Print detailed information (within the given class) about all geoms (if no additional arguments were specified) or the given geoms. This command is only available if the given class exists in the kernel. Additional options include: -a Print information for geoms without providers. status Print general information (within the given class) about all geoms (if no additional arguments were specified) or the given geoms. This command is only available if the given class exists in the kernel. Additional options include: -a When used with -g, print status for geoms without providers. -g Report statuses for geoms instead of providers. -s Produce script-friendly output. load Load the kernel module that implements the given class. This command is only available if the class does not yet exist in the kernel and the file geom_<class>.ko can be found in one of the directories specified in kern.module_path sysctl. unload Unload the kernel module which implements the given class. This command is only available if the given class is loaded as a kernel module. Class-specific commands are implemented as shared libraries which are stored in /lib/geom/ directory and are loaded via dlopen(3) function when the class name is known. When a class-specific shared library exists, a direct utility should also be available under the name of gclass. Currently available classes which are aware of geom(8): o CACHE o CONCAT o ELI o JOURNAL o LABEL o MIRROR o MOUNTVER o MULTIPATH o NOP o PART o RAID o RAID3 o SCHED o SHSEC o STRIPE o VIRSTOR ENVIRONMENT
The following environment variables affect the execution of geom: GEOM_LIBRARY_PATH Specifies the path where shared libraries are stored instead of /lib/geom/. Multiple paths can be specified with a colon- separated list of paths. EXIT STATUS
Exit status is 0 on success, and 1 if the command fails. EXAMPLES
The following example shows how to set up a stripe on three disks for automatic configuration: geom stripe label -v -s 65536 data /dev/da0 /dev/da1 /dev/da2 or: gstripe label -v -s 65536 data /dev/da0 /dev/da1 /dev/da2 Print the list of all providers from the DISK class: geom disk list Unload a kernel module which implements the MD class: geom md unload SEE ALSO
libgeom(3), geom(4), gcache(8), gconcat(8), geli(8), gjournal(8), glabel(8), gmirror(8), gmountver(8), gmultipath(8), gnop(8), gpart(8), graid3(8), gsched(8), gshsec(8), gstripe(8), gvirstor(8) HISTORY
The geom utility appeared in FreeBSD 5.3. AUTHORS
Pawel Jakub Dawidek <pjd@FreeBSD.org> BSD
January 5, 2011 BSD