MULTIPATH.CONF(5)						File Formats Manual						 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  imple-
			mented 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/tar-
				    get*/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.

       prio		The  default program and args to path priority routine. The specified routine should return a numeric value specifying the
			relative priority of this path. Higher number have a higher priority.

			alua	    Generate the path priority based on ALUA status of the path.

			aas	    Generate the path priority based on ALUA status of the path, taking into account the 'PREF' setting.

			weightedpath <hbtl|devname> <regex1> <prio1> <regex2> <prio2> ...
				    hbtl regex can be of SCSI H:B:T:L format  Ex: 1:0:.:. , *:0:0:.  devname regex can be of  device  name  format
				    Ex:  sda  , sd.e Generate the path priority based on the regular expression and the priority provided as argu-
				    ment.

       features 	Specify any device-mapper features to be used. Syntax is num list where num is the number of features in  list.   Possible
			values for the feature list are

			queue_if_no_path
				    Queue IO if no path is active; identical to the no_path_retry keyword.

			no_partitions
				    Disable automatic partitions generation via kpartx.

       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 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 /var/lib/multipath/bindings to assign a persistent and unique alias to the  multi-
			path,  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.  bindings_file The full pathname of the binding file to be
			used when the user_friendly_names option is set. Defaults to /var/lib/multipath/bindings

       dev_loss_tmo	The default dev_loss_tmo setting for an FC remote port in seconds. If an rport has vanished from the fabric all devices on
			that port will be removed from sysfs after this timeout. Default is 10.

       fast_io_fail_tmo The default fast_io_fail_tmo setting for an FC remote port in seconds. If an rport has vanished from the fabric all I/O to
			the devices on that port will be terminated after this timeout. Should be smaller than dev_loss_tmo setting. Default is 5.

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 or devices section:

	      path_grouping_policy
	      path_selector
	      prio
	      failback
	      no_path_retry
	      rr_min_io
	      features

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
	      prio
	      features
	      prio_callout
	      failback
	      rr_weight
	      no_path_retry
	      rr_min_io
	      dev_loss_tmo
	      fast_io_fail_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@free.fr> and others.

								 30 November 2006						 MULTIPATH.CONF(5)