Provided by: multipath-tools_0.7.4-2ubuntu3.2_amd64 
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.