bionic (5) multipath.conf.5.gz
NAME
multipath.conf - multipath daemon configuration file.
DESCRIPTION
/etc/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. Currently used multipathd configuration can be displayed with the multipath -t or multipathd show config command.
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 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
The defaults section recognizes the following keywords:
verbosity Default verbosity. Higher values increase the verbosity level. Valid levels are between
0 and 6.
The default is: 2
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.
The default is: 5
max_polling_interval
Maximal interval between two path checks in seconds.
The default is: 4 * polling_interval
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.
The default is: no
multipath_dir Directory where the dynamic shared objects are stored. Defined at compile time, commonly
/lib64/multipath/ or /lib/multipath/.
The default is: <system dependent>
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 I/O to
each. Some aspects of behavior can be controlled with the attributes:
rr_min_io, rr_min_io_rq and rr_weight.
queue-length 0
(Since 2.6.31 kernel) Choose the path for the next bunch of I/O based on the
amount of outstanding I/O to the path.
service-time 0
(Since 2.6.31 kernel) Choose the path for the next bunch of I/O based on the
amount of outstanding I/O to the path and its relative throughput.
The default is: service-time 0
path_grouping_policy
The default path grouping policy to apply to unspecified multipaths. Possible values
are:
failover One path per priority group.
multibus All paths in one priority group.
group_by_serial
One priority group per serial number.
group_by_prio
One 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
One priority group per target node name. Target node names are fetched in
/sys/class/fc_transport/target*/node_name.
The default is: failover
uid_attrs The udev attribute providing a unique path identifier for corresponding type of path
devices. If this field is configured and matched with type of device, it would override
any other methods providing for device unique identifier in config file, and it would
activate merging uevents according to the identifier to promote effiecncy in processing
uevents. It has no default value, if you want to identify path by udev attribute and to
activate merging uevents for SCSI and DASD devices, you can set its value as: uid_attrs
"sd:ID_SERIAL dasd:ID_UID".
The default is: <unset>
uid_attribute The udev attribute providing a unique path identifier.
The default is: for SCSI devices ID_SERIAL
The default is: for DASD devices ID_UID
The default is: for NVME devices ID_WWN
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.
The default is: <unset>
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:
const Return a constant priority of 1.
sysfs Use the sysfs attributes access_state and preferred_path to generate the
path priority. This prioritizer accepts the optional prio_arg
exclusive_pref_bit.
emc (Hardware-dependent) Generate the path priority for DGC class arrays as
CLARiiON CX/AX and EMC VNX and Unity families.
alua (Hardware-dependent) Generate the path priority based on the SCSI-3 ALUA
settings. This prioritizer accepts the optional prio_arg exclusive_pref_bit.
ontap (Hardware-dependent) Generate the path priority for NetApp ONTAP class and
OEM arrays as IBM NSeries.
rdac (Hardware-dependent) Generate the path priority for LSI/Engenio/NetApp RDAC
class as NetApp SANtricity E/EF Series, and OEM arrays from IBM DELL SGI STK
and SUN.
hp_sw (Hardware-dependent) Generate the path priority for HP/COMPAQ/DEC HSG80 and
MSA/HSV arrays with Active/Standby mode exclusively.
hds (Hardware-dependent) Generate the path priority for Hitachi AMS 2000 and HUS
100 families of 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.
path_latency
Generate the path priority based on a latency algorithm. Requires prio_args
keyword.
datacore (Hardware-dependent) Generate the path priority for some DataCore storage
arrays. Requires prio_args keyword.
iet (iSCSI only) Generate path priority for iSCSI targets based on IP address.
Requires prio_args keyword.
The default depends on the detect_prio setting: If detect_prio is yes (default), the
default priority algorithm is sysfs (except for NetAPP E-Series, where it is alua). If
detect_prio is no, the default priority algorithm is const.
prio_args Arguments to pass to to the prio function. This only applies to certain prioritizers:
weighted Needs a value of the form "<hbtl|devname|serial|wwn> <regex1> <prio1>
<regex2> <prio2> ..."
hbtl Regex can be of SCSI H:B:T:L format. For example: 1:0:.:. , *:0:0:.
devname Regex can be of device name format. For example: sda , sd.e
serial Regex can be of serial number format. For example: .*J1FR.*324 . The
serial can be looked up through sysfs or by running multipathd show
paths format "%z". For example: 0395J1FR904324
wwn Regex can be of the form
"host_wwnn:host_wwpn:target_wwnn:target_wwpn" these values can be
looked up through sysfs or by running multipathd show paths format
"%N:%R:%n:%r". For example:
0x200100e08ba0aea0:0x210100e08ba0aea0:.*:.* ,
.*:.*:iqn.2009-10.com.redhat.msp.lab.ask-06:.*
path_latency
Needs a value of the form "io_num=<20> base_num=<10>"
io_num The number of read IOs sent to the current path continuously, used
to calculate the average path latency. Valid Values: Integer, [2,
200].
base_num
The base number value of logarithmic scale, used to partition
different priority ranks. Valid Values: Integer, [2, 10]. And Max
average latency value is 100s, min average latency value is 1us.
For example: If base_num=10, the paths will be grouped in priority
groups with path latency <=1us, (1us, 10us], (10us, 100us], (100us,
1ms], (1ms, 10ms], (10ms, 100ms], (100ms, 1s], (1s, 10s], (10s,
100s], >100s.
alua If exclusive_pref_bit is set, paths with the preferred path bit set will
always be in their own path group.
sysfs If exclusive_pref_bit is set, paths with the preferred path bit set will
always be in their own path group.
datacore
preferredsds
(Mandatory) The preferred "SDS name".
timeout (Optional) The timeout for the INQUIRY, in ms.
iet
preferredip=...
(Mandatory) Th preferred IP address, in dotted decimal notation, for
iSCSI targets.
The default is: <unset>
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:
queue_if_no_path
(Deprecated, superseded by no_path_retry) Queue I/O if no path is active.
Identical to the no_path_retry with queue value. If both this feature and
no_path_retry are set, the latter value takes precedence. See KNOWN ISSUES.
pg_init_retries <times>
(Since kernel 2.6.24) Number of times to retry pg_init, it must be between 1
and 50.
pg_init_delay_msecs <msecs>
(Since kernel 2.6.38) Number of msecs before pg_init retry, it must be
between 0 and 60000.
queue_mode <mode>
(Since kernel 4.8) Select the the queueing mode per multipath device.
<mode> can be bio, rq or mq, which corresponds to bio-based, request-based,
and block-multiqueue (blk-mq) request-based, respectively. The default
depends on the kernel parameter dm_mod.use_blk_mq. It is mq if the latter is
set, and rq otherwise.
The default is: <unset>
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 tur instead.
tur Issue a TEST UNIT READY command to the device.
emc_clariion
(Hardware-dependent) Query the DGC/EMC specific EVPD page 0xC0 to determine
the path state for CLARiiON CX/AX and EMC VNX and Unity arrays families.
hp_sw (Hardware-dependent) Check the path state for HP/COMPAQ/DEC HSG80 and
MSA/HSV arrays with Active/Standby mode exclusively.
rdac (Hardware-dependent) Check the path state for LSI/Engenio/NetApp RDAC class
as NetApp SANtricity E/EF Series, and OEM arrays from IBM DELL SGI STK and
SUN.
directio (Deprecated) Read the first sector with direct I/O. This checker is being
deprecated, it could cause spurious path failures under high load. Please
use tur instead.
cciss_tur (Hardware-dependent) Check the path state for HP/COMPAQ Smart Array(CCISS)
controllers.
none Do not check the device, fallback to use the values retrieved from sysfs
rbd Check if the path is in the Ceph blacklist and remap the path if it is.
The default is: tur
alias_prefix The user_friendly_names prefix.
The default is: mpath
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.
immediate Immediately failback to the highest priority pathgroup that contains active
paths.
manual Do not perform automatic failback.
followover Used to deal with multiple computers accessing the same Active/Passive
storage devices. Only perform automatic failback when the first path of a
pathgroup becomes active. This keeps a cluster node from automatically
failing back when another node requested the failover.
values > 0 Deferred failback (time to defer in seconds).
The default is: manual
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.
The default is: 1000
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.
The default is: 1
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.
The default is: max
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.
The default is: uniform
no_path_retry Specify what to do when all paths are down. Possible values are:
value > 0 Number of retries until disable I/O queueing.
fail For immediate failure (no I/O queueing).
queue For never stop I/O queueing, similar to queue_if_no_path. See KNOWN ISSUES.
The default is: fail
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.
The default is: no
checker_timeout Specify the timeout to use for path checkers and prioritizers that issue SCSI commands
with an explicit timeout, in seconds.
The default is: in /sys/block/sd<x>/device/timeout
flush_on_last_del
If set to yes , multipathd will disable queueing when the last path to a device has been
deleted.
The default is: no
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.
The default is: no
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.
The default is: in 5
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 600 if
fast_io_fail_tmo is not set. See KNOWN ISSUES.
The default is: 600
bindings_file The full pathname of the binding file to be used when the user_friendly_names option is
set.
The default is: /etc/multipath/bindings
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.
The default is: /etc/multipath/wwids
prkeys_file The full pathname of the prkeys file, which is used by multipathd to keep track of the
persistent reservation key used for a specific WWID, when reservation_key is set to
file.
The default is /etc/multipath/prkeys
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.
The default is: always
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.
Alternatively, this can be set to file, which will store the RESERVATION KEY registered
by mpathpersist in the prkeys_file. multipathd will then use this key to register
additional paths as they appear. When the registration is removed, the RESERVATION KEY
is removed from the prkeys_file.
The default is: <unset>
retain_attached_hw_handler
(Obsolete for kernels >= 4.3) 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.
The default is: yes
Important Note: Linux kernel 4.3 or newer always behaves as if
"retain_attached_hw_handler yes" was set.
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.
The default is: yes
detect_checker if set to yes , multipath will try to detect if the device supports SCSI-3 ALUA. If so,
the device will automatically use the tur checker. If set to no , the checker will be
selected as usual.
The default is: yes
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.
The default is: no
strict_timing 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.
The default is: no
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.
The default is: no
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.
The default is: <unset>
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.
The default is: /etc/multipath/conf.d/
marginal_path_double_failed_time
One of the four parameters of supporting path check based on accounting IO error such as
intermittent error. When a path failed event occurs twice in
marginal_path_double_failed_time seconds due to an IO error and all the other three
parameters are set, multipathd will fail the path and enqueue this path into a queue of
which members are sent a couple of continuous direct reading asynchronous IOs at a fixed
sample rate of 10HZ to start IO error accounting process.
The default is: no
marginal_path_err_sample_time
One of the four parameters of supporting path check based on accounting IO error such as
intermittent error. If it is set to a value no less than 120, when a path fail event
occurs twice in marginal_path_double_failed_time second due to an IO error, multipathd
will fail the path and enqueue this path into a queue of which members are sent a couple
of continuous direct reading asynchronous IOs at a fixed sample rate of 10HZ to start
the IO accounting process for the path will last for marginal_path_err_sample_time. If
the rate of IO error on a particular path is greater than the
marginal_path_err_rate_threshold, then the path will not reinstate for
marginal_path_err_rate_threshold seconds unless there is only one active path. After
marginal_path_err_recheck_gap_time expires, the path will be requeueed for rechecking.
If checking result is good enough, the path will be reinstated.
The default is: no
marginal_path_err_rate_threshold
The error rate threshold as a permillage (1/1000). One of the four parameters of
supporting path check based on accounting IO error such as intermittent error. Refer to
marginal_path_err_sample_time. If the rate of IO errors on a particular path is greater
than this parameter, then the path will not reinstate for
marginal_path_err_rate_threshold seconds unless there is only one active path.
The default is: no
marginal_path_err_recheck_gap_time
One of the four parameters of supporting path check based on accounting IO error such as
intermittent error. Refer to marginal_path_err_sample_time. If this parameter is set to
a positive value, the failed path of which the IO error rate is larger than
marginal_path_err_rate_threshold will be kept in failed state for
marginal_path_err_recheck_gap_time seconds. When marginal_path_err_recheck_gap_time
seconds expires, the path will be requeueed for checking. If checking result is good
enough, the path will be reinstated, or else it will keep failed.
The default is: no
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.
The default is: no
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.
The default is: no
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 remember 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.
The default is: no
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.
The default is: 1000
retrigger_tries Sets the number of times multipathd will try to retrigger a uevent to get the WWID.
The default is: 3
retrigger_delay Sets the amount of time, in seconds, to wait between retriggers.
The default is: 10
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.
The default is: 30
skip_kpartx If set to yes , kpartx will not automatically create partitions on the device.
The default is: no
disable_changed_wwids
If set to yes, multipathd will check the path wwid on change events, and if it has
changed from the wwid of the multipath device, multipathd will disable access to the
path until the wwid changes back.
The default is: no
remove_retries This sets how may times multipath will retry removing a device that is in-use. Between
each attempt, multipath will sleep 1 second.
The default is: 0
max_sectors_kb Sets the max_sectors_kb device parameter on all path devices and the multipath device to
the specified value.
The default is: <device dependent>
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:
devnode Regular expression of the device nodes to be excluded.
The default is: ^(ram|raw|loop|fd|md|dm-|sr|scd|st|dcssblk)[0-9] and ^(td|hd|vd)[a-z]
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 blacklist_exceptions section is used to revert the actions of the blacklist section. For example 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:
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.
The default is: (SCSI_IDENT_|ID_WWN)
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 only recognized attribute for the multipaths section is the multipath subsection.
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:
path_grouping_policy
path_selector
prio
prio_args
failback
rr_weight
no_path_retry
rr_min_io
rr_min_io_rq
flush_on_last_del
features
reservation_key
user_friendly_names
deferred_remove
marginal_path_err_sample_time
marginal_path_err_rate_threshold
marginal_path_err_recheck_gap_time
marginal_path_double_failed_time
delay_watch_checks
delay_wait_checks
skip_kpartx
max_sectors_kb
devices section
The only recognized attribute for the devices section is the device subsection.
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:
1 emc (Hardware-dependent) Hardware handler for DGC class arrays as CLARiiON CX/AX
and EMC VNX and Unity families.
1 rdac (Hardware-dependent) Hardware handler for LSI/Engenio/NetApp RDAC class as
NetApp SANtricity E/EF Series, and OEM arrays from IBM DELL SGI STK and SUN.
1 hp_sw (Hardware-dependent) Hardware handler for HP/COMPAQ/DEC HSG80 and MSA/HSV
arrays with Active/Standby mode exclusively.
1 alua (Hardware-dependent) Hardware handler for SCSI-3 ALUA compatible arrays.
The default is: <unset>
Important Note: Linux kernels 4.3 and newer automatically attach a device handler to
known devices (which includes all devices supporting SCSI-3 ALUA) and disallow changing
the handler afterwards. Setting hardware_handler for such devices on these kernels has
no effect.
The following attributes are optional; if not set the default values are taken from the defaults section:
path_grouping_policy
uid_attribute
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
retain_attached_hw_handler
detect_prio
detect_checker
deferred_remove
marginal_path_err_sample_time
marginal_path_err_rate_threshold
marginal_path_err_recheck_gap_time
marginal_path_double_failed_time
delay_watch_checks
delay_wait_checks
skip_kpartx
max_sectors_kb
overrides section
The overrides section recognizes the following optional attributes; if not set the values are taken from
the devices or defaults sections:
path_grouping_policy
uid_attribute
getuid_callout
path_selector
path_checker
alias_prefix
features
prio
prio_args
failback
rr_weight
no_path_retry
rr_min_io
rr_min_io_rq
flush_on_last_del
fast_io_fail_tmo
dev_loss_tmo
user_friendly_names
retain_attached_hw_handler
detect_prio
detect_checker
deferred_remove
marginal_path_err_sample_time
marginal_path_err_rate_threshold
marginal_path_err_recheck_gap_time
marginal_path_double_failed_time
delay_watch_checks
delay_wait_checks
skip_kpartx
WWID generation
Multipath uses a World Wide Identification (WWID) to determine which paths belong to the same device.
Each path presenting the same WWID is assumed to point to the same device.
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 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-tools was developed by Christophe Varoqui, <christophe.varoqui@opensvc.com> and others.