.TH MULTIPATH.CONF 5 "30 November 2006" .SH NAME multipath.conf \- multipath daemon configuration file .SH DESCRIPTION .B "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. .SH SYNTAX The configuration file contains entries of the form: .RS .nf .ft B .sp
{ .RS .ft B .I "..." .ft B { .RS .ft B .I "..." .RE } .RE } .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 occor. .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 .I blacklist section. .TP .B multipaths This section defines the multipath topologies. They are indexed by a \fIWorld Wide Identifier\fR(wwid), which is the result of the \fIgetuid_callout\fR program. .TP .B devices This section defines the device-specific settings. .RE .LP .SH "defaults section" The .B defaults section recognizes the following keywords: .TP 17 .B polling_interval interval between two path checks in seconds. For properly functioning paths, the interval between checks will gradually increase to .B max_polling_interval; default is .I 5 .TP .B max_polling_interval maximal interval between two path checks in seconds; default is .I 4 * polling_interval .TP .B udev_dir directory where udev creates its device nodes; default is .I /dev .TP .B multipath_dir directory where the dynamic shared objects are stored; default is system dependent, commonly .I /lib/multipath .TP .B verbosity default verbosity. Higher values increase the verbosity level. Valid levels are between 0 and 6; default is .I 2 .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. Default is .I yes .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 .B "round-robin 0" Loop through every path in the path group, sending the same amount of IO to each. .TP .B "queue-length 0" Send the next bunch of IO down the path with the least amount of outstanding IO. .TP .B "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. .RE .TP .B path_grouping_policy The default path grouping policy to apply to unspecified multipaths. Possible values are .RS .TP 12 .B failover 1 path per priority group .TP .B multibus all paths in 1 priority group .TP .B group_by_serial 1 priority group per serial number .TP .B group_by_prio 1 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 .B group_by_node_name 1 priority group per target node name. Target node names are fetched in /sys/class/fc_transport/target*/node_name. .TP Default value is \fImultibus\fR. .RE .TP .B 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 .I /lib/udev/scsi_id --whitelisted --replace-whitespace --device=/dev/%n .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. .I "none" is a valid value. Currently the following path priority routines are implemented: .RS .TP 12 .B const Return a constant priority of \fI1\fR. .TP .B emc Generate the path priority for EMC arrays. .TP .B alua Generate the path priority based on the SCSI-3 ALUA settings. .TP .B ontap Generate the path priority for NetApp arrays. .TP .B rdac Generate the path priority for LSI/Engenio/NetApp E-Series RDAC controller. .TP .B hp_sw Generate the path priority for Compaq/HP controller in active/standby mode. .TP .B hds Generate the path priority for Hitachi HDS Modular storage arrays. .TP .B random Generate a random priority between 1 and 10. .TP 12 .B weightedpath Generate the path priority based on the regular expression and the priority provided as argument. requires prio_args keyword. .TP Default value is \fBnone\fR. .RE .TP .B prio_args Arguments to pass to to the prio function. Currently only used with .I weighted, which needs a value of the form .I " ..." .I hbtl regex can be of SCSI H:B:T:L format Ex: 1:0:.:. , *:0:0:. .I devname regex can be of device name format Ex: sda , sd.e .TP .B features Specify any device-mapper features to be used. Syntax is .I num list where .I num is the number of features in .I list. Possible values for the feature list are .RS .TP 12 .B queue_if_no_path Queue IO if no path is active; identical to the .I no_path_retry keyword. .TP .B no_partitions Disable automatic partitions generation via kpartx. .RE .TP .B path_checker The default method used to determine the paths state. Possible values are .RS .TP 12 .B readsector0 (Deprecated) Read the first sector of the device. This checker is being deprecated, please use \fIdirectio\fR instead .TP .B tur Issue a .I TEST UNIT READY command to the device. .TP .B emc_clariion Query the EMC Clariion specific EVPD page 0xC0 to determine the path state. .TP .B hp_sw Check the path state for HP storage arrays with Active/Standby firmware. .TP .B rdac Check the path state for LSI/Engenio/NetApp E-Series RDAC storage controller. .TP .B directio Read the first sector with direct I/O. .TP Default value is \fIdirectio\fR. .RE .TP .B failback Tell multipathd how to manage path group failback. .RS .TP 12 .B immediate Immediately failback to the highest priority pathgroup that contains active paths. .TP .B manual Do not perform automatic failback. .TP .B values > 0 deferred failback (time to defer in seconds) .TP Default value is \fImanual\fR. .RE .TP .B rr_min_io The number of IO to route to a path before switching to the next in the same path group. This is only for BIO based multipath. Default is .I 1000 .TP .B rr_min_io_q The number of IO requests to route to a path before switching to the next in the same path group. This is only for request based multipath. Default is .I 1 .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 .IR uniform . Default is .IR uniform . .TP .B no_path_retry Specify the number of retries until disable queueing, or .I fail for immediate failure (no queueing), .I queue for never stop queueing. Default is 0. .TP .B user_friendly_names If set to .I yes , using the bindings file .I /etc/multipath/bindings to assign a persistent and unique alias to the multipath, in the form of mpath. 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. Default is .I no .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. Default is .I no .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 /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. .TP .B checker_timeout Specify the timeout to user for path checkers that issue scsi commands with an explicit timeout, in seconds; default taken from .I /sys/block/sd/device/timeout .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 IO to devices on that remote port. This should be smaller than dev_loss_tmo. Setting this to .I off will disable the timeout. .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. .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 IO 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 IO. Setting queue_without_daemon to .I no , avoids this problem. Default is .I yes .TP .B bindings_file The full pathname of the binding file to be used when the user_friendly_names option is set. Defaults to .I /var/lib/multipath/bindings .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. Default is .I always . .SH "blacklist section" The .I 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. .LP The following keywords are recognized: .TP 17 .B wwid The \fIWorld Wide Identification\fR of a device. .TP .B devnode Regular expression of the device nodes to be excluded. .TP .B device Subsection for the device description. This subsection recognizes the .I vendor and .I product keywords. For a full description of these keywords please see the .I devices section description. .SH "blacklist_exceptions section" The .I blacklist_exceptions section is used to revert the actions of the .I blacklist section, ie to include specific device in the multipath topology. This allows one to selectively include devices which would normally be excluded via the .I blacklist section. .LP The following keywords are recognized: .TP 17 .B wwid The \fIWorld Wide Identification\fR of a device. .TP .B devnode Regular expression of the device nodes to be excluded. .TP .B device Subsection for the device description. This subsection recognizes the .I vendor and .I product keywords. For a full description of these keywords please see the .I devices section description. .SH "multipaths section" The only recognized attribute for the .B multipaths section is the .I multipath subsection. .LP The .B multipath subsection recognizes the following attributes: .TP 17 .B wwid Index of the container. Mandatory for this subsection. .TP .B alias (Optional) symbolic name for the multipath map. .LP The following attributes are optional; if not set the default values are taken from the .I defaults or .I devices 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 flush_on_last_del .TP .B no_path_retry .TP .B rr_min_io .TP .B rr_min_io_q .TP .B features .RE .PD .LP .SH "devices section" The only recognized attribute for the .B devices section is the .I device subsection. .LP The .I device subsection recognizes the following attributes: .TP 17 .B vendor (Mandatory) Vendor identifier .TP .B product (Mandatory) Product identifier .TP .B revision (Optional) Revision identfier .TP .B product_blacklist (Optional) Product strings to blacklist for this vendor .TP .B alias_prefix (Optional) The user_friendly_names prefix to use for this device type, instead of the default "mpath" .TP .B hardware_handler (Optional) The hardware handler to use for this device type. The following hardware handler are implemented: .RS .TP 12 .B 1 emc Hardware handler for EMC storage arrays. .TP .B 1 rdac Hardware handler for LSI/Engenio/NetApp E-Series RDAC storage controller. .TP .B 1 hp_sw Hardware handler for Compaq/HP storage arrays in active/standby mode. .TP .B 1 alua Hardware handler for SCSI-3 ALUA compatible arrays. .RE .LP The following attributes are optional; if not set the default values are taken from the .I defaults section: .sp 1 .PD .1v .RS .TP 18 .B path_grouping_policy .TP .B getuid_callout .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 .RE .PD .LP .SH "KNOWN ISSUES" The usage of .B queue_if_no_path option can lead to .B 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 .B no_path_retry option instead. .P The use of .B queue_if_no_path or .B no_path_retry might lead to a deadlock if the .B dev_loss_tmo setting results in a device being removed while I/O is still queued. The multipath daemon will update the .B dev_loss_tmo setting accordingly to avoid this deadlock. Hence if both values are specified the order of precedence is .I no_path_retry, queue_if_no_path, dev_loss_tmo .SH "SEE ALSO" .BR udev (8), .BR dmsetup (8) .BR multipath (8) .BR multipathd (8) .SH AUTHORS .B multipath was developed by Christophe Varoqui, and others.