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mpath_prio_alua (8)
  • >> mpath_prio_alua (8) ( Linux man: Команды системного администрирования )
  •  

    NAME

    mpath_prio_alua - Path priority tool based on Asymmetric LUn Access
     
    

    SYNOPSIS

    mpath_prio_alua [-d directory] [-h] [-v] [-V] device [ device [ ... ]]  

    DESCRIPTION

    mpath_prio_alua is used as a priority callout for the multipath command. It returns a number that is used by multipath to group devices with the same priority together.  

    OPTIONS

    -d directory
    target directory for devices given as relative device names or devices given as major:minor
     number. Default is "/dev".
    -h
    displays the command line help.
    -v
    turns on verbose output. This shows all results in human readable format. This includes information about the port group the device is in and its current state.
    -V
    shows the version number and exits.
    device
    specifies the device to query (the device must be a SCSI device that supports the lq]Report Target Port Groupsrq] command). One of the following three formats may be used:
    *
    The full path name that starts with '/' (e.g. /dev/sda).
    *
    The device name only. This will prefix the directory name given by the -d option (e.g. sda).
    *
    The major and minor number of the device separated by ':'. This will create a temporary device node in the device directory (e.g. 8:0). The temporary name will be lq]tmpdev-<major>:<minor>-<pid>rq].
     

    RETURN VALUE

    The mpath_prio_alua command returns the following values:
    0
    on success. In this case the priority for the device is printed to stdout. The priority value is:
    50
    for devices that are in the active, optimized group
    10
    for devices that are in an active but non-optimized group
    1
    for devices that are in the standby group
    0
    for all other groups
    The reason for the widely spaced priority values is the way multipath handles them. It will multiply the number of paths in a group with the priority value and select the group with the highest result. Thus, if there are six paths in the active, non-optimized group and only one in the active, optimized one, the non-optimized group would be used.
    1
    Indicates an error parsing the command line.
    2
    The given devices could not be opened for reading.
    3
    The device does not support target port groups.
    4
    The inquiry command did not return a target port group for the given device.
    5
    The report target port group command failed or did not return a target port group that was obtained from the inquiry command.
     

    EXAMPLES

    This example queries a device directly and returns the priority string:
    #> mpath_prio_alua /dev/sda
    50
    Now the major and minor number is used to specify the device and verbose output is selected:
    #> mpath_prio_alua -v 8:0
    Target port groups are implicitly supported.
    Reported target port group is 0 [active/optimized]
    50
    The following example shows the entries in the devices section of the multipath-tool configuration file (/etc/multipath.conf) to support an IBM DS6000 storage system:
    device {
    vendor
    "IBM "
    product
    "1750500 "
    path_grouping_policy
    group_by_prio
    prio_callout
    "/sbin/mpath_prio_alua -d/tmp %d"
    features
    "1 queue_if_no_path"
    path_checker
    tur
    }
    Notes:
    *
    Depending on your default configuration not all keywords are required (e.g. if your path_checker is set to tur you don't have to use the path_checker statement in the device section).
    *
    The entries for vendor and product must be strings that are 8 characters long (for vendor) and 16 characters long (for product). The strings have to be padded with blanks if necessary.
    *
    If you are working with hotpluggable devices whose device nodes are created by udev you should use the %d flag in the prio_callout statement. This is because a short time elapses between the devices being available and udev creating the device nodes.
    *
    If under certain circumstances your storage subsystem temporarily reports failures on all paths, you should use the features statement showed in the example. This will configure the multipath volume to requeue I/O until a path becomes available again, instead of reporting failures in that case.
     

    SEE ALSO

    multipath(8),  

    AUTHORS

    mpath_prio_alua was developed by Jan Kunigk and adapted by Stefan Bader <[email protected]>


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    OPTIONS
    RETURN VALUE
    EXAMPLES
    SEE ALSO
    AUTHORS


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