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multipath.conf(5) [linux man page]

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 values are given in the appropriate device or multipath sections. 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 max_polling_interval; default is 5 max_polling_interval maximal interval between two path checks in seconds; default is 4 * polling_interval udev_dir directory where udev creates its device nodes; default is /dev multipath_dir directory where the dynamic shared objects are stored; default is system dependent, commonly /lib/multipath verbosity default verbosity. Higher values increase the verbosity level. Valid levels are between 0 and 6; default is 2 reassign_maps enable reassigning of device-mapper maps. With this option multipathd will remap existing device-mapper maps to always point to multipath device, not the underlying block devices. Possible values are yes and no. Default is yes path_selector The default path selector algorithm to use; they are offered by the kernel multipath target. There are three selector algorithms. round-robin 0 Loop through every path in the path group, sending the same amount of IO to each. queue-length 0 Send the next bunch of IO down the path with the least amount of outstanding IO. service-time 0 Choose the path for the next bunch of IO based on the amount of outstanding IO to the path and its relative throughput. 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 --replace-whitespace --device=/dev/%n prio The name of the path priority routine. The specified routine should return a numeric value specifying the relative prior- ity of this path. Higher number have a higher priority. none is a valid value. Currently the following path priority rou- tines are implemented: const Return a constant priority of 1. emc Generate the path priority for EMC arrays. alua Generate the path priority based on the SCSI-3 ALUA settings. ontap Generate the path priority for NetApp arrays. rdac Generate the path priority for LSI/Engenio/NetApp E-Series RDAC controller. hp_sw Generate the path priority for Compaq/HP controller in active/standby mode. hds Generate the path priority for Hitachi HDS Modular storage arrays. random Generate a random priority between 1 and 10. weightedpath Generate the path priority based on the regular expression and the priority provided as argument. requires prio_args keyword. Default value is none. prio_args Arguments to pass to to the prio function. Currently only used with weighted, which needs a value of the form <hbtl|dev- name> <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 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 (Deprecated) Read the first sector of the device. This checker is being deprecated, please use directio instead 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/NetApp E-Series RDAC storage controller. directio Read the first sector with direct I/O. Default value is directio. failback Tell multipathd how to manage path group failback. immediate Immediately failback to the highest priority pathgroup that contains active paths. manual Do not perform automatic failback. values > 0 deferred failback (time to defer in seconds) 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. This is only for BIO based multi- path. Default is 1000 rr_min_io_q The number of IO requests to route to a path before switching to the next in the same path group. This is only for request based multipath. Default is 1 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 overridden by any spe- cific aliases in the multipaths section. Default is no flush_on_last_del If set to yes , multipathd will disable queueing when the last path to a device has been deleted. 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. checker_timeout Specify the timeout to user for path checkers that issue scsi commands with an explicit timeout, in seconds; default taken from /sys/block/sd<x>/device/timeout 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 fail- ing 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 remov- ing 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 bindings_file The full pathname of the binding file to be used when the user_friendly_names option is set. Defaults to /var/lib/multi- path/bindings log_checker_err If set to once , multipathd logs the first path checker error at logging level 2. Any later errors are logged at level 3 until the device is restored. If set to always , multipathd always logs the path checker error at logging level 2. Default is always 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 one 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 prio_args failback rr_weight flush_on_last_del no_path_retry rr_min_io rr_min_io_q 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 revision (Optional) Revision identfier product_blacklist (Optional) Product strings to blacklist for this vendor alias_prefix (Optional) The user_friendly_names prefix to use for this device type, instead of the default "mpath" 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. 1 rdac Hardware handler for LSI/Engenio/NetApp E-Series RDAC storage controller. 1 hp_sw Hardware handler for Compaq/HP storage arrays in active/standby mode. 1 alua Hardware handler for SCSI-3 ALUA compatible 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 prio_args features failback rr_weight no_path_retry rr_min_io rr_min_io_rq fast_io_fail_tmo dev_loss_tmo flush_on_last_del 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. The use of queue_if_no_path or no_path_retry might lead to a deadlock if the dev_loss_tmo setting results in a device being removed while I/O is still queued. The multipath daemon will update the dev_loss_tmo setting accordingly to avoid this deadlock. Hence if both values are specified the order of precedence is no_path_retry, queue_if_no_path, dev_loss_tmo SEE ALSO
udev(8), dmsetup(8) multipath(8) multipathd(8) AUTHORS
multipath was developed by Christophe Varoqui, <christophe.varoqui@opensvc.com> and others. 30 November 2006 MULTIPATH.CONF(5)
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