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$FreeBSD: head/sbin/geom/class/mirror/gmirror.8 133959 2004-08-18 15:54:52Z pjd $
.Dd Jul 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 .Op Ar prov Op Ar ... .Nm .Cm clear .Op Fl v .Ar prov .Op Ar prov Op Ar ... .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 .Op Ar prov Op Ar ... .Nm .Cm insert .Op Fl hipv .Ar name .Ar prov .Op Ar prov Op Ar ... .Nm .Cm remove .Op Fl v .Ar name .Ar prov .Op Ar prov Op Ar ... .Nm .Cm activate .Op Fl v .Ar name .Ar prov .Op Ar prov Op Ar ... .Nm .Cm deactivate .Op Fl v .Ar name .Ar prov .Op Ar prov Op Ar ... .Nm .Cm forget .Op Fl v .Ar name .Op Ar name Op Ar ... .Nm .Cm stop .Op Fl fv .Ar name .Op Ar name Op Ar ... .Nm .Cm list .Op Ar name Op Ar ... .Nm .Cm load .Op Fl v .Nm .Cm unload .Op Fl v .Sh DESCRIPTION The .Nm utility is used for mirrors (RAID1) configuration. After a mirror creation, all components are detected and configured automatically. All operations like failure detection, stale components detection, rebuild of stale components etc. are done automatically as well. The .Nm utility uses on-disk metadata (the last provider's 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. Components order is important, because priority is based on its position (starting from 0). Component with the biggest priority is used by prefer balance algorithm and also is used as a master component when resynchronization is needed after, e.g. a power failure if 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 "round-robin" t load Read from the component with the lowest load. t prefer Read from the component with the biggest priority. t round-robin Use round-robin algorithm when choosing component to read. t 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 .Nm split balance algorithm and I/O READ request is bigger than or equal to this value, 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 .Nm split balance algorithm. .El t Cm rebuild Rebuild the given mirror components forcibly. If autosynchronization wasn't turn off for the given device, this command hopefully will not be used. t Cm insert Add the given component(s) to the existing mirror. Additional options include: l -tag -width ".Fl h" t Fl h Hardcode providers' names in metadata. t Fl i Mark component(s) as inacitve immediatelly after insertion. t Fl p 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 disk failed and can't be reconnected, so .Cm remove command can't be used to remove it. t Cm stop Stop the given mirror. Additional options include: l -tag -width ".Fl f" t Fl f Stop the given mirror even if it is opened. .El t Cm list List every currently configured devices, 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 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 sunchronization 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 da3 .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 (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 DIAGNOSTICS Exit status is 0 on success, and 1 if the command fails. .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 component's priority inside a running mirror.