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gmirror (8)
  • >> gmirror (8) ( FreeBSD man: Команды системного администрирования )
  • Ключ gmirror обнаружен в базе ключевых слов.

  • BSD mandoc
     

    NAME

    
    
    gmirror
    
     - control utility for mirrored devices
    
     
    

    SYNOPSIS

    label [-Fhnv ] [-b balance ] [-s slice ] name prov ...
    clear [-v ] prov ...
    configure [-adfFhnv ] [-b balance ] [-s slice ] name
    rebuild [-v ] name prov ...
    insert [-hiv ] [-p priority ] name prov ...
    remove [-v ] name prov ...
    activate [-v ] name prov ...
    deactivate [-v ] name prov ...
    forget [-v ] name ...
    stop [-fv ] name ...
    dump prov ...
    list
    status
    load
    unload  

    DESCRIPTION

    The 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 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.

    The first argument to indicates an action to be performed:

    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.

    Additional options include:

    -b balance
    Specifies balance algorithm to use, one of:

    load
    Read from the component with the lowest load.
    prefer
    Read from the component with the biggest priority.
    round-robin
    Use round-robin algorithm when choosing component to read.
    split
    Split read requests, which are bigger than or equal to slice size on N pieces, where N is the number of active components. This is the default balance algorithm.

    -F
    Do not synchronize after a power failure or system crash. Assumes device is in consistent state.
    -h
    Hardcode providers' names in metadata.
    -n
    Turn off autosynchronization of stale components.
    -s slice
    When using the 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 components. Defaults to 4096 bytes.

    clear
    Clear metadata on the given providers.
    configure
    Configure the given device.

    Additional options include:

    -a
    Turn on autosynchronization of stale components.
    -b balance
    Specifies balance algorithm to use.
    -d
    Do not hardcode providers' names in metadata.
    -f
    Synchronize device after a power failure or system crash.
    -F
    Do not synchronize after a power failure or system crash. Assumes device is in consistent state.
    -h
    Hardcode providers' names in metadata.
    -n
    Turn off autosynchronization of stale components.
    -s slice
    Specifies slice size for split balance algorithm.

    rebuild
    Rebuild the given mirror components forcibly. If autosynchronization was not turned off for the given device, this command should be unnecessary.
    insert
    Add the given component(s) to the existing mirror.

    Additional options include:

    -h
    Hardcode providers' names in metadata.
    -i
    Mark component(s) as inactive immediately after insertion.
    -p priority
    Specifies priority of the given component(s).

    remove
    Remove the given component(s) from the mirror and clear metadata on it.
    activate
    Activate the given component(s), which were marked as inactive before.
    deactivate
    Mark the given component(s) as inactive, so it will not be automatically connected to the mirror.
    forget
    Forget about components which are not connected. This command is useful when a disk has failed and cannot be reconnected, preventing the remove command from being used to remove it.
    stop
    Stop the given mirror.

    Additional options include:

    -f
    Stop the given mirror even if it is opened.

    dump
    Dump metadata stored on the given providers.
    list
    See geom(8).
    status
    See geom(8).
    load
    See geom(8).
    unload
    See geom(8).

    Additional options include:

    -v
    Be more verbose.

     

    EXIT STATUS

    Exit status is 0 on success, and 1 if the command fails.  

    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:
    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
    

    Create a mirror on disk with valid data (note that the last sector of the disk will be overwritten). Add another disk to this mirror, so it will be synchronized with existing disk:

    gmirror label -v -b round-robin data da0
    gmirror insert data da1
    

    Create a mirror, but do not use automatic synchronization feature. Add another disk and rebuild it:

    gmirror label -v -n -b load data da0 da1
    gmirror insert data da2
    gmirror rebuild data da2
    

    One disk failed. Replace it with a brand new one:

    gmirror forget data
    gmirror insert data da1
    

    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):

    gmirror label data da0 da1
    gmirror deactivate data da1
    dd if=/dev/da1 of=/backup/data.img bs=1m
    gmirror activate data da1
    
     

    NOTES

    Doing kernel dumps to providers.

    This is possible, but some conditions have to be met. First of all, a kernel dump will go only to one component and always chooses the component with the highest priority. Reading a dump from the mirror on boot will only work if the prefer balance algorithm is used (that way will read only from the component with the highest priority). If you use a different balance algorithm, you should add:

    gmirror configure -b prefer data
    

    to the /etc/rc.early script and:

    gmirror configure -b round-robin data
    

    to the /etc/rc.local script. The decision which component to choose for dumping is made when dumpon(8) is called. If on the next boot a component with a higher priority will be available, the prefer algorithm will choose to read from it and savecore(8) will find nothing. If on the next boot a component with the highest priority will be synchronized, the prefer balance algorithm will read from the next one, thus will find nothing there.  

    SEE ALSO

    geom(4), dumpon(8), geom(8), mount(8), newfs(8), savecore(8), umount(8), vinum(8)  

    HISTORY

    The utility appeared in Fx 5.3 .  

    AUTHORS

    An Pawel Jakub Dawidek Aq [email protected]  

    BUGS

    There should be a way to change a component's priority inside a running mirror.

    There should be a section with an implementation description.

    Documentation for sysctls kern.geom.mirror.* is missing.


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    EXIT STATUS
    EXAMPLES
    NOTES
    SEE ALSO
    HISTORY
    AUTHORS
    BUGS


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