MULTIPATH.CONF(5)MULTIPATH.CONF(5)NAMEmultipath.conf - multipath daemon configuration file
DESCRIPTIONmultipath.conf is the configuration file for the multipath daemon. It
is used to overwrite the built-in configuration table of multipathd.
Any line whose first non-white-space character is a '#' is considered a
comment line. Empty lines are ignored.
SYNTAX
The configuration file contains entries of the form:
<section> {
<attribute> <value>
...
<subsection> {
<attribute> <value>
...
}
}
Each section contains one or more attributes or subsections. The recog‐
nized keywords for attributes or subsections depend on the section in
which they occor.
The following section keywords are recognized:
defaults This section defines default settings for devices-map‐
per-multipath. These values can be overwritten by the
devices and multipaths 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 settings for individual mul‐
tipath devices. These values overwrite what is speci‐
fied in the defaults and devices section of the con‐
figuration file. The devices are identified by the
wwid keyword, which is a regular expression that must
match the result of the getuid_callout program.
devices This section defines the settings for individual stor‐
age controller types. These value overwrite what is
specified in the defaults section of the configuration
file. These controller types are identified by the
vendor, product, and revision keywords, which are reg‐
ular expressions that must match the sysfs information
about this device. If you are using a storage array
that is not supported by default, you may need to cre‐
ate a devices subsection for your array.
The priority of configuration in multipath.conf is:
multipaths is greater than devices is greater that defaults
defaults section
The defaults section recognizes the following keywords:
polling_interval interval between two path checks in seconds For prop‐
erly functioning paths, the interval between checks
will gradually increase to (4 * polling_interval);
default is 5
udev_dir directory where udev creates its device nodes; default
is /dev
multipath_dir directory where the dynamic shared objects are stored;
default is system dependent, commonly /lib/multipath
find_multipaths If set to yes , instead of trying to create a multi‐
path 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 multi‐
path command, or 3 a path has the same WWID as a mul‐
tipath device that was previously created while
find_multipaths was set (even if that multipath device
doesn't currently exist). Whenever a multipath device
is created with find_multipaths set, multipath will
remeber the WWID of the device, so that it will auto‐
matically 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; Default is no
verbosity default verbosity. Higher values increase the ver‐
bosity level. Valid levels are between 0 and 6;
default is 2
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 IO to each.
queue-length 0
Send the next bunch of IO down the path
with the least amount of outstanding IO.
service-time 0
Choose the path for the next bunch of IO
based on the amount of outstanding IO to
the path and its relative throughput.
path_grouping_policy
The default path grouping policy to apply to unspeci‐
fied multipaths. Possible values are
failover 1 path per priority group
multibus all paths in 1 priority group
group_by_serial
1 priority group per serial number
group_by_prio
1 priority group per priority value. Pri‐
orities are determined by callout programs
specified as a global, per-controller or
per-multipath option in the configuration
file.
group_by_node_name
1 priority group per target node name.
Target node names are fetched in
/sys/class/fc_transport/target*/node_name.
Default value is multibus.
getuid_callout The default program and args to callout to obtain a
unique path identifier. Should be specified with an
absolute path. Default value is /lib/udev/scsi_id
--whitelisted --device=/dev/%n
prio The default method used to obtain a path priority
value. Possible values are
const Set a priority of one to all paths
emc Generate the path priority for EMC arrays
alua Generate the path priority based on the
SCSI-3 ALUA settings.
tpg_pref Generate the path prority based on the
SCSI-3 ALUA settings, using the preferred
port bit.
ontap Generate the path priority for NetApp
arrays.
rdac Generate the path priority for LSI/Enge‐
nio/NetApp E-Series RDAC controller.
hp_sw Generate the path priority for Compaq/HP
controller in active/standby mode.
hds Generate the path priority for Hitachi HDS
Modular storage arrays.
Default value is const.
features Specify any device-mapper features to be used. Syntax
is num list where num is the number of features in
list. Possible values for the feature list are
queue_if_no_path
Queue IO if no path is active; identical
to the no_path_retry keyword.
no_partitions
Disable automatic partitions generation
via kpartx.
path_checker The default method used to determine the paths' state.
Possible values are
readsector0 Read the first sector of the device
tur Issue a TEST UNIT READY command to the
device.
emc_clariion
Query the EMC Clariion specific EVPD page
0xC0 to determine the path state.
hp_sw Check the path state for HP storage arrays
with Active/Standby firmware.
rdac Check the path state for LSI/Enge‐
nio/NetApp E-Series RDAC storage con‐
troller.
directio Read the first sector with direct I/O.
Default value is readsector0.
failback Tell multipathd how to manage path group failback.
immediate Immediately failback to the highest prior‐
ity pathgroup that contains active paths.
manual Do not perform automatic failback.
followover Only perform automatic failback when the
first path of a pathgroup becomes active.
This keeps a node from automatically fail‐
ing back when another node requested the
failover.
values > 0 deferred failback (time to defer in sec‐
onds)
Default value is manual.
rr_min_io The number of IO to route to a path before switching
to the next in the same path group, using bio-based
device-mapper-multipath. This is only for systems run‐
ning kernels older that 2.6.31. Newer systems should
use rr_min_io_rq. Default is 1000
rr_min_io_rq The number of IO to route to a path before switching
to the next in the same path group, using request-
based device-mapper-multipath. This setting should be
used on systems running current kernels. On systems
running kernels older than 2.6.31, use rr_min_io.
Default is 1
rr_weight If set to priorities the multipath configurator will
assign path weights as "path prio * rr_min_io". Possi‐
ble values are priorities or uniform uniform
no_path_retry Specify the number of retries until disable queueing,
or fail for immediate failure (no queueing), queue for
never stop queueing. Default is 0.
user_friendly_names
If set to yes , using the bindings file /etc/multi‐
path/bindings to assign a persistent and unique alias
to the multipath, in the form of mpath<n>. If set to
no use the WWID as the alias. In either case this be
will be overriden by any specific aliases in the mul‐
tipaths section. Default is no
queue_without_daemon
If set to no , multipathd will disable queueing for
all devices when it is shut down. Default is yes
flush_on_last_del
If set to yes , multipathd will disable queueing when
the last path to a device has been deleted. Default is
no
max_fds Specify the maximum number of file descriptors that
can be opened by multipath and multipathd. This is
equivalent to ulimit -n. A value of max will set this
to the system limit from /proc/sys/fs/nr_open. If this
is not set, the maximum number of open fds is taken
from the calling process. It is usually 1024. To be
safe, this should be set to the maximum number of
paths plus 32, if that number is greated than 1024.
checker_timeout Specify the timeout to user for path checkers that
issue scsi commands with an explict timeout, in sec‐
onds; default taken from /sys/block/sd<x>/device/time‐
out
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 IO to devices on that remote port.
This should be smaller than dev_loss_tmo. Setting this
to off will disable the timeout.
dev_loss_tmo Specify the number of seconds the scsi layer will wait
after a problem has been detected on a FC remote port
before removing it from the system. This can be set to
"infinity" which sets it to the max value of
2147483647 seconds, or 68 years.
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. Default is always
hwtable_regex_match
If set to yes , user device configs will be regular
expression matched against the builtin configs to
determine if they should modify an existing config or
create a new one. If set to no , user device configs
will be string matched against the builtin configs to
determine if they should modify an existing config or
create a new one. Default is no
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 PERSIS‐
TENT 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. It is unset
by default.
retain_attached_hw_handler
If set to yes and the scsi layer has already attached
a hardware_handler to the device, multipath will not
force the device to use the hardware_handler specified
by mutipath.conf. If the scsi layer has not attached a
hardware handler, multipath will continue to use its
configured hardware handler. Default is no
detect_prio If set to yes , multipath will try to detect if the
device supports ALUA. If so, the device will automati‐
cally use the alua prioritizer. If not, the priori‐
tizer will be selected as usual. Default is no
reload_readwrite If set to yes , multipathd will monitor change events
on path devices. When it receives a change event for
a path of a readonly multipath device, it will check
if the path is now read/write. If so, multipathd will
reload the multipath device to switch it to
read/write. Default is no
replace_wwid_whitespace
If set to yes devices using the default getuid callout
(scsi_id) will add --relace-whitespace to the callout
line. This will cause any whitespace in the wwid to
be replaced with one underscore.
blacklist section
The blacklist section is used to exclude specific device from inclusion
in the multipath topology. It is most commonly used to exclude local
disks or LUNs for the array controller.
The following keywords are recognized:
wwid The World Wide Identification of a device.
devnode Regular expression of the device nodes to be excluded.
device Subsection for the device description. This subsection
recognizes the vendor and product keywords. For a full
description of these keywords please see the devices
section description.
blacklist_exceptions section
The blacklist_exceptions section is used to revert the actions of the
blacklist section, ie to include specific device in the multipath
topology. This allows to selectively include devices which would nor‐
mally be excluded via the blacklist section.
The following keywords are recognized:
wwid The World Wide Identification of a device.
devnode Regular expression of the device nodes to be excluded.
device Subsection for the device description. This subsection
recognizes the vendor and product keywords. For a full
description of these keywords please see the devices
section description.
multipaths section
The only recognized attribute for the multipaths section is the multi‐
path subsection.
The multipath subsection recognizes the following attributes:
wwid Index of the container. Mandatory for this subsection.
alias (Optional) symbolic name for the multipath map.
The following attributes are optional; if not set the default values
are taken from the defaults section:
path_grouping_policy
path_selector
failback
prio
no_path_retry
rr_min_io
rr_min_io_rq
rr_weight
flush_on_last_del
reservation_key
devices section
The only recognized attribute for the devices section is the device
subsection.
The device subsection recognizes the following attributes:
vendor (Mandatory) Vendor identifier
product (Mandatory) Product identifier
revision Revision identifier
product_blacklist
Product strings to blacklist for this vendor
hardware_handler (Optional) The hardware handler to use for this device
type. The following hardware handler are implemented:
1 emc Hardware handler for EMC storage arrays.
1 alua Hardware handler for SCSI-3 ALUA arrays.
1 hp_sw Hardware handler for Compaq/HP con‐
trollers.
1 rdac Hardware handler for the LSI/Enge‐
nio/NetApp E-Series RDAC storage con‐
troller.
The following attributes are optional; if not set the default values
are taken from the defaults section:
path_grouping_policy
getuid_callout
path_selector
path_checker
features
prio
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
KNOWN ISSUES
The usage of queue_if_no_path option can lead to D state processes
being hung and not killable in situations where all the paths to the
LUN go offline. It is advisable to use the no_path_retry option
instead.
SEE ALSOudev(8), dmsetup(8)multipath(8)multipathd(8)AUTHORS
multipath was developed by Christophe Varoqui, <christophe.varo‐
qui@free.fr> and others.
30 November 2006 MULTIPATH.CONF(5)
