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$FreeBSD: head/sbin/geom/class/mirror/gmirror.8 143535 2005-03-13 19:38:12Z pjd $
.Dd July 9, 2004 .Dt GMIRROR 8 .Os .Sh NAME .Nm gmirror .Nd "control utility for mirrored devices" .Sh SYNOPSIS .Nm .Cm label .Op Fl hnv .Op Fl b Ar balance .Op Fl s Ar slice .Ar name .Ar prov ... .Nm .Cm clear .Op Fl v .Ar prov ... .Nm .Cm configure .Op Fl adhnv .Op Fl b Ar balance .Op Fl s Ar slice .Ar name .Nm .Cm rebuild .Op Fl v .Ar name .Ar prov ... .Nm .Cm insert .Op Fl hiv .Op Fl p Ar priority .Ar name .Ar prov ... .Nm .Cm remove .Op Fl v .Ar name .Ar prov ... .Nm .Cm activate .Op Fl v .Ar name .Ar prov ... .Nm .Cm deactivate .Op Fl v .Ar name .Ar prov ... .Nm .Cm forget .Op Fl v .Ar name ... .Nm .Cm stop .Op Fl fv .Ar name ... .Nm .Cm list .Op Ar name ... .Nm .Cm status .Op Ar name ... .Nm .Cm load .Op Fl v .Nm .Cm unload .Op Fl v .Sh DESCRIPTION The .Nm utility is used for mirror (RAID1) configurations. After a mirror's creation, all components are detected and configured automatically. All operations like failure detection, stale component detection, rebuild of stale components, etc. are also done automatically. The .Nm utility uses on-disk metadata (stored in the provider's last sector) to store all needed information. Since the last sector is used for this purpose, it is possible to place a root file system on a mirror.
p The first argument to .Nm indicates an action to be performed: l -tag -width ".Cm deactivate" t Cm label Create a mirror. The order of components is important, because a component's priority is based on its position (starting from 0). The component with the biggest priority is used by the prefer balance algorithm and is also used as a master component when resynchronization is needed, e.g. after a power failure when the device was open for writing.
p Additional options include: l -tag -width ".Fl b Ar balance" t Fl b Ar balance Specifies balance algorithm to use, one of: l -tag -width ".Cm round-robin" t Cm load Read from the component with the lowest load. t Cm prefer Read from the component with the biggest priority. t Cm round-robin Use round-robin algorithm when choosing component to read. t Cm split Split read requests, which are bigger than or equal to slice size on N pieces, where N is the number of active components. .El t Fl h Hardcode providers' names in metadata. t Fl n Turn off autosynchronization of stale components. t Fl s Ar slice When using the .Cm split balance algorithm and an I/O READ request is bigger than or equal to this value, the I/O request will be split into N pieces, where N is the number of active component. .El t Cm clear Clear metadata on the given providers. t Cm configure Configure the given device.
p Additional options include: l -tag -width ".Fl b Ar balance" t Fl a Turn on autosynchronization of stale components. t Fl b Ar balance Specifies balance algorithm to use. t Fl d Do not hardcode providers' names in metadata. t Fl h Hardcode providers' names in metadata. t Fl n Turn off autosynchronization of stale components. t Fl s Ar slice Specifies slice size for .Cm split balance algorithm. .El t Cm rebuild Rebuild the given mirror components forcibly. If autosynchronization was not turned off for the given device, this command should be unnecessary. t Cm insert Add the given component(s) to the existing mirror.
p Additional options include: l -tag -width ".Fl p Ar priority" t Fl h Hardcode providers' names in metadata. t Fl i Mark component(s) as inactive immediately after insertion. t Fl p Ar priority Specifies priority of the given component(s). .El t Cm remove Remove the given component(s) from the mirror and clear metadata on it. t Cm activate Activate the given component(s), which were marked as inactive before. t Cm deactivate Mark the given component(s) as inactive, so it will not be automatically connected to the mirror. t Cm forget Forget about components which are not connected. This command is useful when a disk has failed and cannot be reconnected, preventing the .Cm remove command from being used to remove it. t Cm stop Stop the given mirror.
p Additional options include: l -tag -width ".Fl f" t Fl f Stop the given mirror even if it is opened. .El t Cm list Print detailed information about every currently configured device; if a list of devices is passed as a parameter then only those devices will be shown. t Cm status Print general information about every currently configured device; if a list of devices is passed as a parameter then only those devices will be shown. t Cm load Load
a geom_mirror.ko kernel module. t Cm unload Unload
a geom_mirror.ko kernel module. .El
p Additional options include: l -tag -width ".Fl v" t Fl v Be more verbose. .El .Sh EXIT STATUS Exit status is 0 on success, and 1 if the command fails. .Sh EXAMPLES Use 3 disks to setup a mirror. Choose split balance algorithm, split only requests which are bigger than or equal to 2kB. Create file system, mount it, then unmount it and stop device: d -literal -offset indent gmirror label -v -b split -s 2048 data da0 da1 da2 newfs /dev/mirror/data mount /dev/mirror/data /mnt ... umount /mnt gmirror stop data gmirror unload .Ed
p Create a mirror on disk with valid data. Add another disk to this mirror, so it will be synchronized with existing disk: d -literal -offset indent gmirror label -v -b round-robin data da0 gmirror insert data da1 .Ed
p Create a mirror, but do not use automatic synchronization feature. Add another disk and rebuild it: d -literal -offset indent gmirror label -v -n -b load data da0 da1 gmirror insert data da2 gmirror rebuild data da2 .Ed
p One disk failed. Replace it with a brand new one: d -literal -offset indent gmirror forget data gmirror insert data da1 .Ed
p Create a mirror, deactivate one component, do the backup and connect it again. It will not be resynchronized, if there is no need to do so (there were no writes in the meantime): d -literal -offset indent gmirror label data da0 da1 gmirror deactivate data da1 dd if=/dev/da1 of=/backup/data.img bs=1m gmirror activate data da1 .Ed .Sh SEE ALSO .Xr geom 4 , .Xr geom 8 , .Xr mount 8 , .Xr newfs 8 , .Xr umount 8 , .Xr vinum 8 .Sh HISTORY The .Nm utility appeared in .Fx 5.3 . .Sh AUTHORS .An Pawel Jakub Dawidek Aq pjd@FreeBSD.org .Sh BUGS There should be a way to change a component's priority inside a running mirror.
p There should be a section with an implementation description.
p Documentation for sysctls .Va kern.geom.mirror.* is missing.