MULTIPATH.CONF(5)

NAME
multipath.conf - multipath daemon configuration file

DESCRIPTION
multipath.conf is the configuration file for the multipath daemon. It is used to overwrite the built-in configuration table of multipathd. Any line whose first non-white-space character is a '#' is considered a comment line. Empty lines are ignored.

SYNTAX
The configuration file contains entries of the form:

    <section> {
        <attribute> <value>
        ...
        <subsection> {
            <attribute> <value>
            ...
        }
    }

Each section contains one or more attributes or subsections. The recognized keywords for attributes or subsections depend on the section in which they occor.

The following section keywords are recognized:

defaults
    This section defines default values for attributes which are used whenever no specific setting is given.

blacklist
    This section defines which devices should be excluded from the multipath topology discovery.

blacklist_exceptions
    This section defines which devices should be included in the multipath topology discovery, despite being listed in the blacklist section.

multipaths
    This section defines the multipath topologies. They are indexed by a World Wide Identifier(wwid), which is the result of the getuid_callout program.

devices
    This section defines the device-specific settings.

defaults section
The defaults section recognizes the following keywords:

polling_interval
    interval between two path checks in seconds For properly functioning paths, the interval between checks will gradually increase to (4 * polling_interval); default is 5

udev_dir
    directory where udev creates its device nodes; default is /dev

verbosity
    default verbosity. Higher values increase the verbosity level. Valid levels are between 0 and 6; default is 2

selector
    The default path selector algorithm to use; they are offered by the kernel multipath target. The only currently implemented is round-robin 0

path_grouping_policy
    The default path grouping policy to apply to unspecified multipaths. Possible values are

    failover
        1 path per priority group

    multibus
        all paths in 1 priority group

    group_by_serial
        1 priority group per serial number

    group_by_prio
        1 priority group per priority value. Priorities are determined by callout programs specified as a global, per-controller or per-multipath option in the configuration file.

    group_by_node_name
        1 priority group per target node name. Target node names are fetched in /sys/class/fc_transport/target*/node_name.

    Default value is multibus.

getuid_callout
    The default program and args to callout to obtain a unique path identifier. Should be specified with an absolute path. Default value is /lib/udev/scsi_id --whitelisted --device=/dev/%n

prio_callout
    The default program and args to callout to obtain a path priority value. The specified program will be executed and should return a numeric value specifying the relative priority of this path. Higher number have a higher priority. A '%n' in the command line will be expanded to the device name, a '%b' will be expanded to the device number in major:minor format. none is a valid value. Currently the following path priority programs are implemented:

    mpath_prio_emc /dev/%n
        Generate the path priority for EMC arrays

    mpath_prio_alua /dev/%n
        Generate the path priority based on the SCSI-3 ALUA settings.

    mpath_prio_netapp /dev/%n
        Generate the path priority for NetApp arrays.

    mpath_prio_rdac /dev/%n
        Generate the path priority for LSI/Engenio RDAC controller.

    mpath_prio_hp_sw /dev/%n
        Generate the path priority for Compaq/HP controller in active/standby mode.

    mpath_prio_hds_modular %b
        Generate the path priority for Hitachi HDS Modular storage arrays.

    Default value is none.

features
    Specify any device-mapper features to be used. The most common of these features is 1 queue_if_no_path Note that this can also be set via the no_path_retry keyword.

path_checker
    The default method used to determine the paths' state. Possible values are

    readsector0
        Read the first sector of the device

    tur Issue a TEST UNIT READY command to the device.

    emc_clariion
        Query the EMC Clariion specific EVPD page 0xC0 to determine the path state.

    hp_sw
        Check the path state for HP storage arrays with Active/Standby firmware.

    rdac
        Check the path state for LSI/Engenio RDAC storage controller.

    directio
        Read the first sector with direct I/O.

    Default value is readsector0.

failback
    Tell the daemon to manage path group failback, or not to. 0 or immediate means immediate failback, values >0 means deferred failback (in seconds). manual means no failback. Default value is manual

rr_min_io
    The number of IO to route to a path before switching to the next in the same path group. Default is 1000

rr_weight
    If set to priorities the multipath configurator will assign path weights as "path prio * rr_min_io". Possible values are priorities or uniform. Default is uniform.

no_path_retry
    Specify the number of retries until disable queueing, or fail for immediate failure (no queueing), queue for never stop queueing. Default is 0.

user_friendly_names
    If set to yes , using the bindings file /etc/multipath/bindings to assign a persistent and unique alias to the multipath, in the form of mpath<n>. If set to no use the WWID as the alias. In either case this be will be overriden by any specific aliases in the multipaths section. Default is no

max_fds
    Specify the maximum number of file descriptors that can be opened by multipath and multipathd. This is equivalent to ulimit -n. A value of max will set this to the system limit from /proc/sys/fs/nr_open. If this is not set, the maximum number of open fds is taken from the calling process. It is usually 1024. To be safe, this should be set to the maximum number of paths plus 32, if that number is greated than 1024.

fast_io_fail_tmo
    Specify the number of seconds the scsi layer will wait after a problem has been detected on a FC remote port before failing IO to devices on that remote port. This should be smaller than dev_loss_tmo. Setting this to off will disable the timeout.

dev_loss_tmo
    Specify the number of seconds the scsi layer will wait after a problem has been detected on a FC remote port before removing it from the system.

queue_without_daemon
    If set to no , when multipathd stops, queueing will be turned off for all devices. This is useful for devices that set no_path_retry. If a machine is shut down while all paths to a device are down, it is possible to hang waiting for IO to return from the device after multipathd has been stopped. Without multipathd running, access to the paths cannot be restored, and the kernel cannot be told to stop queueing IO. Setting queue_without_daemon to no , avoids this problem. Default is yes

blacklist section
The blacklist section is used to exclude specific device from inclusion in the multipath topology. It is most commonly used to exclude local disks or LUNs for the array controller.

The following keywords are recognized:

wwid
    The World Wide Identification of a device.

devnode
    Regular expression of the device nodes to be excluded.

device
    Subsection for the device description. This subsection recognizes the vendor and product keywords. For a full description of these keywords please see the devices section description.

blacklist_exceptions section
The blacklist_exceptions section is used to revert the actions of the blacklist section, ie to include specific device in the multipath topology. This allows to selectively include devices which would normally be excluded via the blacklist section.

The following keywords are recognized:

wwid
    The World Wide Identification of a device.

devnode
    Regular expression of the device nodes to be excluded.

device
    Subsection for the device description. This subsection recognizes the vendor and product keywords. For a full description of these keywords please see the devices section description.

multipaths section
The only recognized attribute for the multipaths section is the multipath subsection.

The multipath subsection recognizes the following attributes:

wwid
    Index of the container. Mandatory for this subsection.

alias
    (Optional) symbolic name for the multipath map.

The following attributes are optional; if not set the default values are taken from the defaults section:

    path_grouping_policy

    path_selector

    failback

    no_path_retry

    rr_min_io

devices section
The only recognized attribute for the devices section is the device subsection.

The device subsection recognizes the following attributes:

vendor
    (Mandatory) Vendor identifier

product
    (Mandatory) Product identifier

product_blacklist
    Product strings to blacklist for this vendor

hardware_handler
    (Optional) The hardware handler to use for this device type. The following hardware handler are implemented:

    1 emc
        Hardware handler for EMC storage arrays.

The following attributes are optional; if not set the default values are taken from the defaults section:

    path_grouping_policy

    getuid_callout

    path_selector

    path_checker

    features

    prio_callout

    failback

    rr_weight

    no_path_retry

    rr_min_io

    fast_io_fail_tmo

    dev_loss_tmo

KNOWN ISSUES
The usage of queue_if_no_path option can lead to D state processes being hung and not killable in situations where all the paths to the LUN go offline. It is advisable to use the no_path_retry option instead.

SEE ALSO
udev(8), dmsetup(8) multipath(8) multipathd(8)

AUTHORS
multipath was developed by Christophe Varoqui, <christophe.varoqui@opensvc.com> and others.