.\" ----------------------------------------------------------------------------
.\" Update the date below if you make any significant change.
.\" Make sure there are no errors with:
.\" groff -z -wall -b -e -t multipath/multipath.conf.5
.\" man --warnings -E UTF-8 -l -Tutf8 -Z multipath/multipath.conf.5 >/dev/null
.\"
.\" TODO: Look for XXX and ???
.\"
.\" ----------------------------------------------------------------------------
.
.TH MULTIPATH.CONF 5 2017-08-18 Linux
.
.
.\" ----------------------------------------------------------------------------
.SH NAME
.\" ----------------------------------------------------------------------------
.
multipath.conf \- multipath daemon configuration file.
.
.
.\" ----------------------------------------------------------------------------
.SH DESCRIPTION
.\" ----------------------------------------------------------------------------
.
.B "/etc/multipath.conf"
is the configuration file for the multipath daemon. It is used to
overwrite the built-in configuration table of \fBmultipathd\fP.
Any line whose first non-white-space character is a '#' is considered
a comment line. Empty lines are ignored.
.PP
Currently used multipathd configuration can be displayed with the \fBmultipath -t\fR
or \fBmultipathd show config\fR command.
.
.
.\" ----------------------------------------------------------------------------
.SH SYNTAX
.\" ----------------------------------------------------------------------------
.
The configuration file contains entries of the form:
.RS
.nf
.ft B
.sp
<section> {
.RS
.ft B
<attribute> <value>
.I "..."
.ft B
<subsection> {
.RS
.ft B
<attribute> <value>
.I "..."
.RE
.ft B
}
.RE
.ft B
}
.ft R
.fi
.RE
.LP
Each \fIsection\fP contains one or more attributes or subsections. The
recognized keywords for attributes or subsections depend on the
section in which they occur.
.LP
.
.
The following \fIsection\fP keywords are recognized:
.TP 17
.B defaults
This section defines default values for attributes which are used
whenever no values are given in the appropriate device or multipath
sections.
.TP
.B blacklist
This section defines which devices should be excluded from the
multipath topology discovery.
.TP
.B blacklist_exceptions
This section defines which devices should be included in the
multipath topology discovery, despite being listed in the
\fIblacklist\fR section.
.TP
.B multipaths
This section defines the multipath topologies. They are indexed by a
\fIWorld Wide Identifier\fR(WWID). For details on the WWID generation
see section \fIWWID generation\fR below.
.TP
.B devices
This section defines the device-specific settings.
.TP
.B overrides
This section defines values for attributes that should override the
device-specific settings for all devices.
.RE
.LP
.
.
.\" ----------------------------------------------------------------------------
.SH "defaults section"
.\" ----------------------------------------------------------------------------
.
The \fIdefaults\fR section recognizes the following keywords:
.
.
.TP 17
.B verbosity
Default verbosity. Higher values increase the verbosity level. Valid
levels are between 0 and 6.
.RS
.TP
The default is: \fB2\fR
.RE
.
.
.TP
.B polling_interval
Interval between two path checks in seconds. For properly functioning paths,
the interval between checks will gradually increase to \fImax_polling_interval\fR.
This value will be overridden by the \fIWatchdogSec\fR
setting in the multipathd.service definition if systemd is used.
.RS
.TP
The default is: \fB5\fR
.RE
.
.
.TP
.B max_polling_interval
Maximal interval between two path checks in seconds.
.RS
.TP
The default is: \fB4 * polling_interval\fR
.RE
.
.
.TP
.B 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
\fIyes\fR and \fIno\fR.
.RS
.TP
The default is: \fBno\fR
.RE
.
.
.TP
.B multipath_dir
Directory where the dynamic shared objects are stored. Defined at compile time,
commonly \fI/lib64/multipath/\fR or \fI/lib/multipath/\fR.
.RS
.TP
The default is: \fB<system dependent>\fR
.RE
.
.
.TP
.B path_selector
The default path selector algorithm to use; they are offered by the
kernel multipath target. There are three selector algorithms:
.RS
.TP 12
.I "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:
\fIrr_min_io\fR, \fIrr_min_io_rq\fR and \fIrr_weight\fR.
.TP
.I "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.
.TP
.I "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.
.TP
The default is: \fBservice-time 0\fR
.RE
.
.
.TP
.B path_grouping_policy
The default path grouping policy to apply to unspecified
multipaths. Possible values are:
.RS
.TP 12
.I failover
One path per priority group.
.TP
.I multibus
All paths in one priority group.
.TP
.I group_by_serial
One priority group per serial number.
.TP
.I 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.
.TP
.I group_by_node_name
One priority group per target node name. Target node names are fetched
in \fI/sys/class/fc_transport/target*/node_name\fR.
.TP
The default is: \fBfailover\fR
.RE
.
.
.TP
.B 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: \fIuid_attrs "sd:ID_SERIAL dasd:ID_UID"\fR.
.RS
.TP
The default is: \fB<unset>\fR
.RE
.
.
.TP
.B uid_attribute
The udev attribute providing a unique path identifier.
.RS
.TP
The default is: for SCSI devices \fBID_SERIAL\fR
.TP
The default is: for DASD devices \fBID_UID\fR
.TP
The default is: for NVME devices \fBID_WWN\fR
.RE
.
.
.TP
.B getuid_callout
(Superseded by \fIuid_attribute\fR) The default program and args to callout
to obtain a unique path identifier. Should be specified with an absolute path.
.RS
.TP
The default is: \fB<unset>\fR
.RE
.
.
.TP
.B 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.
\fI"none"\fR is a valid value. Currently the following path priority routines
are implemented:
.RS
.TP 12
.I const
Return a constant priority of \fI1\fR.
.TP
.I sysfs
Use the sysfs attributes \fIaccess_state\fR and \fIpreferred_path\fR to
generate the path priority. This prioritizer accepts the optional prio_arg
\fIexclusive_pref_bit\fR.
.TP
.I emc
(Hardware-dependent)
Generate the path priority for DGC class arrays as CLARiiON CX/AX and
EMC VNX and Unity families.
.TP
.I alua
(Hardware-dependent)
Generate the path priority based on the SCSI-3 ALUA settings. This prioritizer
accepts the optional prio_arg \fIexclusive_pref_bit\fR.
.TP
.I ontap
(Hardware-dependent)
Generate the path priority for NetApp ONTAP class and OEM arrays as IBM NSeries.
.TP
.I 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.
.TP
.I hp_sw
(Hardware-dependent)
Generate the path priority for HP/COMPAQ/DEC HSG80 and MSA/HSV arrays with
Active/Standby mode exclusively.
.TP
.I hds
(Hardware-dependent)
Generate the path priority for Hitachi AMS 2000 and HUS 100 families of arrays.
.TP
.I random
Generate a random priority between 1 and 10.
.TP
.I weightedpath
Generate the path priority based on the regular expression and the
priority provided as argument. Requires prio_args keyword.
.TP
.I path_latency
Generate the path priority based on a latency algorithm.
Requires prio_args keyword.
.TP
.I datacore
(Hardware-dependent)
Generate the path priority for some DataCore storage arrays. Requires prio_args
keyword.
.TP
.I iet
(iSCSI only)
Generate path priority for iSCSI targets based on IP address. Requires
prio_args keyword.
.PP
The default depends on the \fBdetect_prio\fR setting: If \fBdetect_prio\fR is
\fByes\fR (default), the default priority algorithm is \fBsysfs\fR (except for
NetAPP E-Series, where it is \fBalua\fR). If \fBdetect_prio\fR is
\fBno\fR, the default priority algorithm is \fBconst\fR.
.RE
.
.
.TP
.B prio_args
Arguments to pass to to the prio function. This only applies to certain
prioritizers:
.RS
.TP 12
.I weighted
Needs a value of the form
\fI"<hbtl|devname|serial|wwn> <regex1> <prio1> <regex2> <prio2> ..."\fR
.RS
.TP 8
.I hbtl
Regex can be of SCSI H:B:T:L format. For example: 1:0:.:. , *:0:0:.
.TP
.I devname
Regex can be of device name format. For example: sda , sd.e
.TP
.I 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
.TP
.I wwn
Regex can be of the form \fI"host_wwnn:host_wwpn:target_wwnn:target_wwpn"\fR
these values can be looked up through sysfs or by running \fImultipathd show paths format
"%N:%R:%n:%r"\fR. For example: 0x200100e08ba0aea0:0x210100e08ba0aea0:.*:.* , .*:.*:iqn.2009-10.com.redhat.msp.lab.ask-06:.*
.RE
.TP 12
.I path_latency
Needs a value of the form "io_num=\fI<20>\fR base_num=\fI<10>\fR"
.RS
.TP 8
.I 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].
.TP
.I 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.
.RE
.TP 12
.I alua
If \fIexclusive_pref_bit\fR is set, paths with the \fIpreferred path\fR bit
set will always be in their own path group.
.TP
.I sysfs
If \fIexclusive_pref_bit\fR is set, paths with the \fIpreferred path\fR bit
set will always be in their own path group.
.TP
.I datacore
.RS
.TP 8
.I preferredsds
(Mandatory) The preferred "SDS name".
.TP
.I timeout
(Optional) The timeout for the INQUIRY, in ms.
.RE
.TP 12
.I iet
.RS
.TP 8
.I preferredip=...
(Mandatory) Th preferred IP address, in dotted decimal notation, for iSCSI targets.
.RE
.TP
The default is: \fB<unset>\fR
.RE
.
.
.TP
.B features
Specify any device-mapper features to be used. Syntax is \fInum list\fR
where \fInum\fR is the number, between 0 and 8, of features in \fIlist\fR.
Possible values for the feature list are:
.RS
.TP 12
.I queue_if_no_path
(Deprecated, superseded by \fIno_path_retry\fR) Queue I/O if no path is active.
Identical to the \fIno_path_retry\fR with \fIqueue\fR value. If both this
feature and \fIno_path_retry\fR are set, the latter value takes
precedence. See KNOWN ISSUES.
.TP
.I pg_init_retries <times>
(Since kernel 2.6.24) Number of times to retry pg_init, it must be between 1 and 50.
.TP
.I pg_init_delay_msecs <msecs>
(Since kernel 2.6.38) Number of msecs before pg_init retry, it must be between 0 and 60000.
.TP
.I queue_mode <mode>
(Since kernel 4.8) Select the the queueing mode per multipath device.
<mode> can be \fIbio\fR, \fIrq\fR or \fImq\fR, which corresponds to
bio-based, request-based, and block-multiqueue (blk-mq) request-based,
respectively.
The default depends on the kernel parameter \fBdm_mod.use_blk_mq\fR. It is
\fImq\fR if the latter is set, and \fIrq\fR otherwise.
.TP
The default is: \fB<unset>\fR
.RE
.
.
.TP
.B path_checker
The default method used to determine the paths state. Possible values
are:
.RS
.TP 12
.I readsector0
(Deprecated) Read the first sector of the device. This checker is being
deprecated, please use \fItur\fR instead.
.TP
.I tur
Issue a \fITEST UNIT READY\fR command to the device.
.TP
.I 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.
.TP
.I hp_sw
(Hardware-dependent)
Check the path state for HP/COMPAQ/DEC HSG80 and MSA/HSV arrays with
Active/Standby mode exclusively.
.TP
.I 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.
.TP
.I 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 \fItur\fR instead.
.TP
.I cciss_tur
(Hardware-dependent)
Check the path state for HP/COMPAQ Smart Array(CCISS) controllers.
.TP
.I none
Do not check the device, fallback to use the values retrieved from sysfs
.TP
.I rbd
Check if the path is in the Ceph blacklist and remap the path if it is.
.TP
The default is: \fBtur\fR
.RE
.
.
.TP
.B alias_prefix
The \fIuser_friendly_names\fR prefix.
.RS
.TP
The default is: \fBmpath\fR
.RE
.
.
.TP
.B failback
Tell multipathd how to manage path group failback.
To select \fIimmediate\fR or a \fIvalue\fR, it's mandatory that the device
has support for a working prioritizer.
.RS
.TP 12
.I immediate
Immediately failback to the highest priority pathgroup that contains
active paths.
.TP
.I manual
Do not perform automatic failback.
.TP
.I 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.
.TP
.I values > 0
Deferred failback (time to defer in seconds).
.TP
The default is: \fBmanual\fR
.RE
.
.
.TP
.B  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 \fIBlock I/O\fR(BIO) based multipath and
only apply to \fIround-robin\fR path_selector.
.RS
.TP
The default is: \fB1000\fR
.RE
.
.
.TP
.B 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 \fIRequest\fR based multipath and
only apply to \fIround-robin\fR path_selector.
.RS
.TP
The default is: \fB1\fR
.RE
.
.
.TP
.B 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 \fImax\fR will set
this to the system limit from \fI/proc/sys/fs/nr_open\fR. 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.
.RS
.TP
The default is: \fBmax\fR
.RE
.
.
.TP
.B rr_weight
If set to \fIpriorities\fR the multipath configurator will assign path weights
as "path prio * rr_min_io". Possible values are
.I priorities
or
.I uniform .
Only apply to \fIround-robin\fR path_selector.
.RS
.TP
The default is: \fBuniform\fR
.RE
.
.
.TP
.B no_path_retry
Specify what to do when all paths are down. Possible values are:
.RS
.TP 12
.I value > 0
Number of retries until disable I/O queueing.
.TP
.I fail
For immediate failure (no I/O queueing).
.TP
.I queue
For never stop I/O queueing, similar to \fIqueue_if_no_path\fR. See KNOWN ISSUES.
.TP
The default is: \fBfail\fR
.RE
.
.
.TP
.B queue_without_daemon
If set to
.I 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
.I no
, avoids this problem.
.RS
.TP
The default is: \fBno\fR
.RE
.
.
.TP
.B checker_timeout
Specify the timeout to use for path checkers and prioritizers that issue SCSI
commands with an explicit timeout, in seconds.
.RS
.TP
The default is: in \fB/sys/block/sd<x>/device/timeout\fR
.RE
.
.
.TP
.B flush_on_last_del
If set to
.I yes
, multipathd will disable queueing when the last path to a device has been
deleted.
.RS
.TP
The default is: \fBno\fR
.RE
.
.
.TP
.B user_friendly_names
If set to
.I yes
, using the bindings file \fI/etc/multipath/bindings\fR to assign a persistent
and unique alias to the multipath, in the form of mpath<n>. If set to
.I no
use the WWID as the alias. In either case this be will
be overridden by any specific aliases in the \fImultipaths\fR section.
.RS
.TP
The default is: \fBno\fR
.RE
.
.
.TP
.B 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
.I off
will disable the timeout.
.RS
.TP
The default is: in \fB5\fR
.RE
.
.
.TP
.B 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 \fIno_path_retry\fR * \fIpolling_interval\fR
if a number of retries is given with \fIno_path_retry\fR and the
overall retry interval is longer than the specified \fIdev_loss_tmo\fR value.
The Linux kernel will cap this value to \fI600\fR if \fIfast_io_fail_tmo\fR
is not set. See KNOWN ISSUES.
.RS
.TP
The default is: \fB600\fR
.RE
.
.
.TP
.B bindings_file
The full pathname of the binding file to be used when the user_friendly_names
option is set.
.RS
.TP
The default is: \fB/etc/multipath/bindings\fR
.RE
.
.
.TP
.B 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.
.RS
.TP
The default is: \fB/etc/multipath/wwids\fR
.RE
.
.
.TP
.B 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
\fIreservation_key\fR is set to \fBfile\fR.
.RS
.TP
The default is \fB/etc/multipath/prkeys\fR
.RE
.
.
.TP
.B log_checker_err
If set to
.I 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
.I always
, multipathd always logs the path checker error at logging level 2.
.RS
.TP
The default is: \fBalways\fR
.RE
.
.
.TP
.B 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.
.RS
.PP
Alternatively, this can be set to \fBfile\fR, which will store the RESERVATION
KEY registered by mpathpersist in the \fIprkeys_file\fR. 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
\fIprkeys_file\fR.
.TP
The default is: \fB<unset>\fR
.RE
.
.
.TP
.B retain_attached_hw_handler
(Obsolete for kernels >= 4.3) If set to
.I 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.
.RS
.PP
The default is: \fByes\fR
.PP
\fBImportant Note:\fR Linux kernel 4.3 or newer always behaves as if
\fB"retain_attached_hw_handler yes"\fR was set.
.RE
.
.
.TP
.B detect_prio
If set to
.I yes
, multipath will try to detect if the device supports SCSI-3 ALUA. If so, the
device will automatically use the \fIsysfs\fR prioritizer if the required sysf
attributes \fIaccess_state\fR and \fIpreferred_path\fR are supported, or the
\fIalua\fR prioritizer if not. If set to
.I no
, the prioritizer will be selected as usual.
.RS
.TP
The default is: \fByes\fR
.RE
.
.
.TP
.B detect_checker
if set to
.I yes
, multipath will try to detect if the device supports SCSI-3 ALUA. If so, the
device will automatically use the \fItur\fR checker. If set to
.I no
, the checker will be selected as usual.
.RS
.TP
The default is: \fByes\fR
.RE
.
.
.TP
.B force_sync
If set to
.I 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.
.RS
.TP
The default is: \fBno\fR
.RE
.
.
.TP
.B strict_timing
If set to
.I yes
, multipathd will start a new path checker loop after exactly one second,
so that each path check will occur at exactly \fIpolling_interval\fR
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 \fIpolling_interval\fR
seconds.
.RS
.TP
The default is: \fBno\fR
.RE
.
.
.TP
.B deferred_remove
If set to
.I 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.
.RS
.TP
The default is: \fBno\fR
.RE
.
.
.TP
.B 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 \fI"p"\fR to names ending in a
number. If this parameter is set, multipath will act like kpartx does with
the \fI-p\fR option is used, and always add delimiter.
.RS
.TP
The default is: \fB<unset>\fR
.RE
.
.
.TP
.B 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 \fI/etc/multipath.conf\fR.
config_dir must either be "" or a fully qualified directory name.
.RS
.TP
The default is: \fB/etc/multipath/conf.d/\fR
.RE
.
.
.TP
.B 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
\fImarginal_path_double_failed_time\fR 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.
.RS
.TP
The default is: \fBno\fR
.RE
.
.
.TP
.B 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 \fImarginal_path_double_failed_time\fR
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
\fImarginal_path_err_sample_time\fR.
If the rate of IO error on a particular path is greater than the
\fImarginal_path_err_rate_threshold\fR, then the path will not reinstate for
\fImarginal_path_err_recheck_gap_time\fR seconds unless there is only one
active path. After \fImarginal_path_err_recheck_gap_time\fR expires, the path
will be requeueed for rechecking. If checking result is good enough, the
path will be reinstated.
.RS
.TP
The default is: \fBno\fR
.RE
.
.
.TP
.B 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 \fImarginal_path_err_sample_time\fR. If the rate of IO errors
on a particular path is greater than this parameter, then the path will not
reinstate for \fImarginal_path_err_rate_threshold\fR seconds unless there is
only one active path.
.RS
.TP
The default is: \fBno\fR
.RE
.
.
.TP
.B 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
\fImarginal_path_err_sample_time\fR. If this parameter is set to a positive
value, the failed path of  which the IO error rate is larger than
\fImarginal_path_err_rate_threshold\fR will be kept in failed state for
\fImarginal_path_err_recheck_gap_time\fR seconds. When
\fImarginal_path_err_recheck_gap_time\fR 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.
.RS
.TP
The default is: \fBno\fR
.RE
.
.
.TP
.B 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 \fIdelay_wait_checks\fR checks.
.RS
.TP
The default is: \fBno\fR
.RE
.
.
.TP
.B delay_wait_checks
If set to a value greater than 0, when a device that has recently come back
online fails again within \fIdelay_watch_checks\fR checks, the next time it
comes back online, it will marked and delayed, and not used until it has passed
\fIdelay_wait_checks\fR checks.
.RS
.TP
The default is: \fBno\fR
.RE
.
.
.TP
.B find_multipaths
If set to
.I 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.
.I 1
There are at least two non-blacklisted paths with the same WWID,
.I 2
the user manually forces the creation, by specifying a device with the multipath
command, or
.I 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.
.RS
.TP
The default is: \fBno\fR
.RE
.
.
.TP
.B 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.
.RS
.TP
The default is: \fB1000\fR
.RE
.
.
.TP
.B retrigger_tries
Sets the number of times multipathd will try to retrigger a uevent to get the
WWID.
.RS
.TP
The default is: \fB3\fR
.RE
.
.
.TP
.B retrigger_delay
Sets the amount of time, in seconds, to wait between retriggers.
.RS
.TP
The default is: \fB10\fR
.RE
.
.
.TP
.B 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.
.RS
.TP
The default is: \fB30\fR
.RE
.
.
.TP
.B skip_kpartx
If set to
.I yes
, kpartx will not automatically create partitions on the device.
.RS
.TP
The default is: \fBno\fR
.RE
.
.
.TP
.B disable_changed_wwids
If set to \fIyes\fR, 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.
.RS
.TP
The default is: \fBno\fR
.RE
.
.
.TP
.B 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.
.RS
.TP
The default is: \fB0\fR
.RE
.
.
.TP
.B max_sectors_kb
Sets the max_sectors_kb device parameter on all path devices and the multipath
device to the specified value.
.RS
.TP
The default is: \fB<device dependent>\fR
.RE
.
.
.TP
.B ghost_delay
Sets the number of seconds that multipath will wait after creating a device
with only ghost paths before marking it ready for use in systemd. This gives
the active paths time to appear before the multipath runs the hardware handler
to switch the ghost paths to active ones. Setting this to \fI0\fR or \fIon\fR
makes multipath immediately mark a device with only ghost paths as ready.
.RS
.TP
The default is \fBno\fR
.RE
.
.
.\" ----------------------------------------------------------------------------
.SH "blacklist section"
.\" ----------------------------------------------------------------------------
.
The \fIblacklist\fR 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.
.LP
.
.
The following keywords are recognized:
.TP 17
.B devnode
Regular expression of the device nodes to be excluded.
.RS
.TP
The default is: \fB^(ram|raw|loop|fd|md|dm-|sr|scd|st|dcssblk)[0-9]\fR and \fB^(td|hd|vd)[a-z]\fR
.RE
.TP
.B wwid
The \fIWorld Wide Identification\fR of a device.
.TP
.B property
Regular expression of the udev property to be excluded.
.TP
.B device
Subsection for the device description. This subsection recognizes the
.B vendor
and
.B product
keywords. For a full description of these keywords please see the
\fIdevices\fR section description.
.
.
.\" ----------------------------------------------------------------------------
.SH "blacklist_exceptions section"
.\" ----------------------------------------------------------------------------
.
The \fIblacklist_exceptions\fR section is used to revert the actions of the
\fIblacklist\fR 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 \fIblacklist\fR section.
.LP
.
.
The following keywords are recognized:
.TP 17
.B devnode
Regular expression of the device nodes to be whitelisted.
.TP
.B wwid
The \fIWorld Wide Identification\fR of a device.
.TP
.B property
Regular expression of the udev property to be whitelisted.
.RS
.TP
The default is: \fB(SCSI_IDENT_|ID_WWN)\fR
.RE
.TP
.B device
Subsection for the device description. This subsection recognizes the
.B vendor
and
.B product
keywords. For a full description of these keywords please see the \fIdevices\fR
section description.
.LP
The \fIproperty\fR blacklist and whitelist handling is different from the usual
handling in the sense that the whitelist \fIhas\fR to be set, otherwise the
device will be blacklisted. In these cases the message \fIblacklisted, udev
property missing\fR will be displayed.
.
.
.\" ----------------------------------------------------------------------------
.SH "multipaths section"
.\" ----------------------------------------------------------------------------
.
The only recognized attribute for the \fImultipaths\fR section is the
\fImultipath\fR subsection.
.LP
.
.
The \fImultipath\fR subsection recognizes the following attributes:
.TP 17
.B wwid
(Mandatory) Index of the container.
.TP
.B alias
Symbolic name for the multipath map.
.LP
.
.
The following attributes are optional; if not set the default values
are taken from the \fIdefaults\fR or \fIdevices\fR section:
.sp 1
.PD .1v
.RS
.TP 18
.B path_grouping_policy
.TP
.B path_selector
.TP
.B prio
.TP
.B prio_args
.TP
.B failback
.TP
.B rr_weight
.TP
.B no_path_retry
.TP
.B rr_min_io
.TP
.B rr_min_io_rq
.TP
.B flush_on_last_del
.TP
.B features
.TP
.B reservation_key
.TP
.B user_friendly_names
.TP
.B deferred_remove
.TP
.B marginal_path_err_sample_time
.TP
.B marginal_path_err_rate_threshold
.TP
.B marginal_path_err_recheck_gap_time
.TP
.B marginal_path_double_failed_time
.TP
.B delay_watch_checks
.TP
.B delay_wait_checks
.TP
.B skip_kpartx
.TP
.B max_sectors_kb
.TP
.B ghost_delay
.RE
.PD
.LP
.
.
.\" ----------------------------------------------------------------------------
.SH "devices section"
.\" ----------------------------------------------------------------------------
.
The only recognized attribute for the \fIdevices\fR section is the \fIdevice\fR
subsection.
.LP
.
.
The \fIdevice\fR subsection recognizes the following attributes:
.TP
vendor, product, revision and product_blacklist are POSIX Extended regex.
.TP 17
.B vendor
(Mandatory) Vendor identifier.
.TP
.B product
(Mandatory) Product identifier.
.TP
.B revision
Revision identfier.
.TP
.B product_blacklist
Product strings to blacklist for this vendor.
.TP
.B alias_prefix
The user_friendly_names prefix to use for this
device type, instead of the default "mpath".
.TP
.B hardware_handler
The hardware handler to use for this device type.
The following hardware handler are implemented:
.RS
.TP 12
.I 1 emc
(Hardware-dependent)
Hardware handler for DGC class arrays as CLARiiON CX/AX and EMC VNX and Unity
families.
.TP
.I 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.
.TP
.I 1 hp_sw
(Hardware-dependent)
Hardware handler for HP/COMPAQ/DEC HSG80 and MSA/HSV arrays with
Active/Standby mode exclusively.
.TP
.I 1 alua
(Hardware-dependent)
Hardware handler for SCSI-3 ALUA compatible arrays.
.PP
The default is: \fB<unset>\fR
.PP
\fBImportant Note:\fR 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 \fBhardware_handler\fR for such devices on these kernels
has no effect.
.RE
.
.
.LP
The following attributes are optional; if not set the default values
are taken from the \fIdefaults\fR
section:
.sp 1
.PD .1v
.RS
.TP 18
.B path_grouping_policy
.TP
.B uid_attribute
.TP
.B path_selector
.TP
.B path_checker
.TP
.B prio
.TP
.B prio_args
.TP
.B features
.TP
.B failback
.TP
.B rr_weight
.TP
.B no_path_retry
.TP
.B rr_min_io
.TP
.B rr_min_io_rq
.TP
.B fast_io_fail_tmo
.TP
.B dev_loss_tmo
.TP
.B flush_on_last_del
.TP
.B retain_attached_hw_handler
.TP
.B detect_prio
.TP
.B detect_checker
.TP
.B deferred_remove
.TP
.B marginal_path_err_sample_time
.TP
.B marginal_path_err_rate_threshold
.TP
.B marginal_path_err_recheck_gap_time
.TP
.B marginal_path_double_failed_time
.TP
.B delay_watch_checks
.TP
.B delay_wait_checks
.TP
.B skip_kpartx
.TP
.B max_sectors_kb
.TP
.B ghost_delay
.RE
.PD
.LP
.
.
.\" ----------------------------------------------------------------------------
.SH "overrides section"
.\" ----------------------------------------------------------------------------
.
The overrides section recognizes the following optional attributes; if not set
the values are taken from the \fIdevices\fR or \fIdefaults\fR sections:
.sp 1
.PD .1v
.RS
.TP 18
.B path_grouping_policy
.TP
.B uid_attribute
.TP
.B getuid_callout
.TP
.B path_selector
.TP
.B path_checker
.TP
.B alias_prefix
.TP
.B features
.TP
.B prio
.TP
.B prio_args
.TP
.B failback
.TP
.B rr_weight
.TP
.B no_path_retry
.TP
.B rr_min_io
.TP
.B rr_min_io_rq
.TP
.B flush_on_last_del
.TP
.B fast_io_fail_tmo
.TP
.B dev_loss_tmo
.TP
.B user_friendly_names
.TP
.B retain_attached_hw_handler
.TP
.B detect_prio
.TP
.B detect_checker
.TP
.B deferred_remove
.TP
.B marginal_path_err_sample_time
.TP
.B marginal_path_err_rate_threshold
.TP
.B marginal_path_err_recheck_gap_time
.TP
.B marginal_path_double_failed_time
.TP
.B delay_watch_checks
.TP
.B delay_wait_checks
.TP
.B skip_kpartx
.TP
.B ghost_delay
.RE
.PD
.LP
.
.
.\" ----------------------------------------------------------------------------
.SH "WWID generation"
.\" ----------------------------------------------------------------------------
.
Multipath uses a \fIWorld Wide Identification\fR (WWID) to determine
which paths belong to the same device. Each path presenting the same
WWID is assumed to point to the same device.
.LP
The WWID is generated by three methods (in the order of preference):
.TP 17
.B getuid_callout
Use the specified external program; cf \fIgetuid_callout\fR 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.
.TP
.B uid_attribute
Use the value of the specified udev attribute; cf \fIuid_attribute\fR
above. This method is preferred to \fIgetuid_callout\fR 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.
.TP
.B vpd_pg83
If none of the \fIgetuid_callout\fR or \fIuid_attribute\fR parameters
are present multipath will try to use the sysfs attribute
\fIvpd_pg83\fR to generate the WWID.
.
.
.\" ----------------------------------------------------------------------------
.SH "KNOWN ISSUES"
.\" ----------------------------------------------------------------------------
.
The usage of \fIqueue_if_no_path\fR option can lead to \fID state\fR
processes being hung and not killable in situations where all the paths to the
LUN go offline. It is advisable to use the \fIno_path_retry\fR option instead.
.P
The use of \fIqueue_if_no_path\fR or \fIno_path_retry\fR might lead to a
deadlock if the \fIdev_loss_tmo\fR setting results in a device being removed
while I/O is still queued. The multipath daemon will update the \fIdev_loss_tmo\fR
setting accordingly to avoid this deadlock. Hence if both values are
specified the order of precedence is \fIno_path_retry, queue_if_no_path, dev_loss_tmo\fR.
.
.
.\" ----------------------------------------------------------------------------
.SH "SEE ALSO"
.\" ----------------------------------------------------------------------------
.
.BR udev (8),
.BR dmsetup (8),
.BR multipath (8),
.BR multipathd (8).
.
.
.\" ----------------------------------------------------------------------------
.SH AUTHORS
.\" ----------------------------------------------------------------------------
.
\fImultipath-tools\fR was developed by Christophe Varoqui, <christophe.varoqui@opensvc.com>
and others.
.\" EOF