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; default
- is 5
- udev_dir directory where udev creates its device nodes; default
- is /dev
- verbosity default verbosity. Higher values increase the ver
- bosity 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 /var/lib/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.
- 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
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.