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
GCONCAT(8) BSD System Manager's Manual GCONCAT(8) NAME
gconcat -- disk concatenation control utility SYNOPSIS
gconcat create [-v] name prov ... gconcat destroy [-fv] name ... gconcat label [-hv] name prov ... gconcat stop [-fv] name ... gconcat clear [-v] prov ... gconcat dump prov ... gconcat list gconcat status gconcat load gconcat unload DESCRIPTION
The gconcat utility is used for device concatenation configuration. The concatenation can be configured using two different methods: ``manual'' or ``automatic''. When using the ``manual'' method, no metadata are stored on the devices, so the concatenated 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 gconcat indicates an action to be performed: create Concatenate the given devices with specified name. This is the ``manual'' method. The kernel module geom_concat.ko will be loaded if it is not loaded already. label Concatenate 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_concat.ko will be loaded if it is not loaded already. stop Turn off existing concatenate 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 concatenated device. -h Hardcode providers' names in metadata. -v Be more verbose. SYSCTL VARIABLES
The following sysctl(8) variables can be used to control the behavior of the CONCAT GEOM class. The default value is shown next to each variable. kern.geom.concat.debug: 0 Debug level of the CONCAT 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. EXAMPLES
The following example shows how to configure four disks for automatic concatenation, create a file system on it, and mount it: gconcat label -v data /dev/da0 /dev/da1 /dev/da2 /dev/da3 newfs /dev/concat/data mount /dev/concat/data /mnt [...] umount /mnt gconcat stop data gconcat unload Configure concatenated provider on one disk only. Create file system. Add two more disks and extend existing file system. gconcat label data /dev/da0 newfs /dev/concat/data gconcat label data /dev/da0 /dev/da1 /dev/da2 growfs /dev/concat/data SEE ALSO
geom(4), loader.conf(5), geom(8), growfs(8), gvinum(8), mount(8), newfs(8), sysctl(8), umount(8) HISTORY
The gconcat utility appeared in FreeBSD 5.3. AUTHORS
Pawel Jakub Dawidek <pjd@FreeBSD.org> BSD
May 21, 2004 BSD