NAME¶

DESCRIPTION¶

SYNTAX¶

<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 occur.

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). For details on the WWID generation see section WWID generation below.

devices

This section defines the device-specific settings.

overrides

This section defines values for attributes that should override the device-specific settings for all devices.

defaults section¶

verbosity

Default verbosity. Higher values increase the verbosity level. Valid levels are between 0 and 6.

polling_interval

Interval between two path checks in seconds. For properly functioning paths, the interval between checks will gradually increase to max_polling_interval. This value will be overridden by the WatchdogSec setting in the multipathd.service definition if systemd is used.

max_polling_interval

Maximal interval between two path checks in seconds.

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.

multipath_dir

Directory where the dynamic shared objects are stored.

path_selector

The default path selector algorithm to use; they are offered by the kernel multipath target. There are three selector algorithms:

path_grouping_policy

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

uid_attribute

The udev attribute providing a unique path identifier.

getuid_callout

(Superseded by uid_attribute) The default program and args to callout to obtain a unique path identifier. Should be specified with an absolute path.

prio

The name of the path priority routine. The specified routine should return a numeric value specifying the relative priority of this path. Higher number have a higher priority. "none" is a valid value. Currently the following path priority routines are implemented:

prio_args

Arguments to pass to to the prio function. This only applies to certain prioritizers:

features

Specify any device-mapper features to be used. Syntax is num list where num is the number, between 0 and 8, of features in list. Possible values for the feature list are:

path_checker

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

alias_prefix

The user_friendly_names prefix.

failback

Tell multipathd how to manage path group failback. To select immediate or a value, it's mandatory that the device has support for a working prioritizer.

rr_min_io

Number of I/O requests to route to a path before switching to the next in the same path group. This is only for Block I/O(BIO) based multipath and only apply to round-robin path_selector.

rr_min_io_rq

Number of I/O requests to route to a path before switching to the next in the same path group. This is only for Request based multipath and only apply to round-robin path_selector.

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.

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 . Only apply to round-robin path_selector.

no_path_retry

Specify what to do when all paths are down. Possible values are:

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 I/O 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 I/O. Setting queue_without_daemon to no , avoids this problem.

checker_timeout

Specify the timeout to use for path checkers and prioritizers that issue SCSI commands with an explicit timeout, in seconds.

flush_on_last_del

If set to yes , multipathd will disable queueing when the last path to a device has been deleted.

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 specific aliases in the multipaths section.

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 I/O 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. This can be set to "infinity" which sets it to the max value of 2147483647 seconds, or 68 years. It will be automatically adjusted to the overall retry interval no_path_retry * polling_interval if a number of retries is given with no_path_retry and the overall retry interval is longer than the specified dev_loss_tmo value. The Linux kernel will cap this value to 300 if fast_io_fail_tmo is not set. See KNOWN ISSUES.

bindings_file

The full pathname of the binding file to be used when the user_friendly_names option is set.

wwids_file

The full pathname of the WWIDs file, which is used by multipath to keep track of the WWIDs for LUNs it has created multipath devices on in the past.

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.

reservation_key

This is the service action reservation key used by mpathpersist. It must be set for all multipath devices using persistent reservations, and it must be the same as the RESERVATION KEY field of the PERSISTENT RESERVE OUT parameter list which contains an 8-byte value provided by the application client to the device server to identify the I_T nexus.

retain_attached_hw_handler

If set to yes and the SCSI layer has already attached a hardware_handler to the device, multipath will not force the device to use the hardware_handler specified by mutipath.conf. If the SCSI layer has not attached a hardware handler, multipath will continue to use its configured hardware handler.

detect_prio

If set to yes , multipath will try to detect if the device supports SCSI-3 ALUA. If so, the device will automatically use the sysfs prioritizer if the required sysf attributes access_state and preferred_path are supported, or the alua prioritizer if not. If set to no , the prioritizer will be selected as usual.

force_sync

If set to yes , multipathd will call the path checkers in sync mode only. This means that only one checker will run at a time. This is useful in the case where many multipathd checkers running in parallel causes significant CPU pressure.

strict_timinig

If set to yes , multipathd will start a new path checker loop after exactly one second, so that each path check will occur at exactly polling_interval seconds. On busy systems path checks might take longer than one second; here the missing ticks will be accounted for on the next round. A warning will be printed if path checks take longer than polling_interval seconds.

deferred_remove

If set to yes , multipathd will do a deferred remove instead of a regular remove when the last path device has been deleted. This means that if the multipath device is still in use, it will be freed when the last user closes it. If path is added to the multipath device before the last user closes it, the deferred remove will be canceled.

partition_delimiter

If this value is not set, when multipath renames a device, it will act just like the kpartx default does, only adding a "p" to names ending in a number. If this parameter is set, multipath will act like kpartx does with the -p option is used, and always add delimiter.

config_dir

If set to anything other than "", multipath will search this directory alphabetically for file ending in ".conf" and it will read configuration information from them, just as if it was in /etc/multipath.conf. config_dir must either be "" or a fully qualified directory name.

delay_watch_checks

If set to a value greater than 0, multipathd will watch paths that have recently become valid for this many checks. If they fail again while they are being watched, when they next become valid, they will not be used until they have stayed up for delay_wait_checks checks.

delay_wait_checks

If set to a value greater than 0, when a device that has recently come back online fails again within delay_watch_checks checks, the next time it comes back online, it will marked and delayed, and not used until it has passed delay_wait_checks checks.

find_multipaths

If set to yes , instead of trying to create a multipath device for every non-blacklisted path, multipath will only create a device if one of three condidions are met. 1 There are at least two non-blacklisted paths with the same WWID, 2 the user manually forces the creation, by specifying a device with the multipath command, or 3 a path has the same WWID as a multipath device that was previously created while find_multipaths was set (even if that multipath device doesn't currently exist). Whenever a multipath device is created with find_multipaths set, multipath will remeber the WWID of the device, so that it will automatically create the device again, as soon as it sees a path with that WWID. This should allow most users to have multipath automatically choose the correct paths to make into multipath devices, without having to edit the blacklist.

uxsock_timeout

CLI receive timeout in milliseconds. For larger systems CLI commands might timeout before the multipathd lock is released and the CLI command can be processed. This will result in errors like "timeout receiving packet" to be returned from CLI commands. In these cases it is recommended to increase the CLI timeout to avoid those issues.

retrigger_tries

Sets the number of times multipathd will try to retrigger a uevent to get the WWID.

retrigger_delay

Sets the amount of time, in seconds, to wait between retriggers.

missing_uev_wait_timeout

Controls how many seconds multipathd will wait, after a new multipath device is created, to receive a change event from udev for the device, before automatically enabling device reloads. Usually multipathd will delay reloads on a device until it receives a change uevent from the initial table load.

skip_kpartx

If set to yes , kpartx will not automatically create partitions on the device.

blacklist section¶

The following keywords are recognized:

devnode

Regular expression of the device nodes to be excluded.

wwid

The World Wide Identification of a device.

property

Regular expression of the udev property 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 following keywords are recognized:

devnode

Regular expression of the device nodes to be whitelisted.

wwid

The World Wide Identification of a device.

property

Regular expression of the udev property to be whitelisted.

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.

The property blacklist and whitelist handling is different from the usual handling in the sense that the whitelist has to be set, otherwise the device will be blacklisted. In these cases the message blacklisted, udev property missing will be displayed.

multipaths section¶

The multipath subsection recognizes the following attributes:

wwid

(Mandatory) Index of the container.

alias

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:

devices section¶

The device subsection recognizes the following attributes:

vendor, product, revision and product_blacklist are POSIX Extended regex.

vendor

(Mandatory) Vendor identifier.

product

(Mandatory) Product identifier.

revision

Revision identfier.

product_blacklist

Product strings to blacklist for this vendor.

alias_prefix

The user_friendly_names prefix to use for this device type, instead of the default "mpath".

hardware_handler

The hardware handler to use for this device type. The following hardware handler are implemented:

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

overrides section¶

WWID generation¶

The WWID is generated by three methods (in the order of preference):

getuid_callout

Use the specified external program; cf getuid_callout above. Care should be taken when using this method; the external program needs to be loaded from disk for execution, which might lead to deadlock situations in an all-paths-down scenario.

uid_attribute

Use the value of the specified udev attribute; cf uid_attribute above. This method is preferred to getuid_callout as multipath does not need to call any external programs here. However, under certain circumstances udev might not be able to generate the requested variable.

vpd_pg83

If none of the getuid_callout or uid_attribute parameters are present multipath will try to use the sysfs attribute vpd_pg83 to generate the WWID.

KNOWN ISSUES¶

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¶

AUTHORS¶