Provided by: multipath-tools_0.5.0+git1.656f8865-5ubuntu2_amd64 bug

NAME

       multipath.conf - multipath daemon configuration file

DESCRIPTION

       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.

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:

       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.  Default
                        is 5

       max_polling_interval
                        maximal  interval  between  two  path  checks  in seconds; default is 4 *
                        polling_interval

       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 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
                        remeber  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;
                        Default is no

       verbosity        default  verbosity.  Higher  values  increase  the verbosity level. Valid
                        levels are between 0 and 6; default is 2

       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.
                        Default is yes

       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 unspecified 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.   Priorities   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 failover.

       uid_attribute    The  udev  attribute providing a unique path identifier. Default value is
                        ID_SERIAL

       getuid_callout   The default  program  and  args  to  callout  to  obtain  a  unique  path
                        identifier. Should be specified with an absolute path.  This parameter is
                        deprecated.

       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.

                        emc         Generate the path priority for EMC arrays.

                        alua        Generate the path priority based on the SCSI-3 ALUA settings.

                        ontap       Generate the path priority for NetApp arrays.

                        rdac        Generate  the  path  priority for LSI/Engenio/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.

                        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.

                        Default value is none.

       prio_args        Arguments to pass to to the prio  function.   Currently  only  used  with
                        weighted, which needs a value of the form <hbtl|devname> <regex1> <prio1>
                        <regex2> <prio2> ...  hbtl regex can  be  of  SCSI  H:B:T:L  format   Ex:
                        1:0:.:.  , *:0:0:.  devname regex can be of device name format  Ex: sda ,
                        sd.e

       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 (Deprecated)  Read  the  first  sector  of  the  device. This
                                    checker is being deprecated, please use directio instead

                        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/Engenio/NetApp  E-Series  RDAC
                                    storage controller.

                        directio    Read the first sector with direct I/O.

                        Default value is directio.

       failback         Tell multipathd how to manage path group failback.

                        immediate   Immediately  failback  to the highest priority 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 failing back when another  node  requested  the
                                    failover.

                        values > 0  deferred failback (time to defer in seconds)

                        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. This is only for BIO based multipath. Default is 1000

       rr_min_io_rq     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 1

       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.
                        Default is uniform.

       no_path_retry    Specify the number  of  retries  until  disable  queueing,  or  fail  for
                        immediate  failure (no queueing), queue for never stop queueing. If unset
                        no queueing is attempted.  Default is unset.

       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.  Default is
                        no

       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 use for path checkers and prioritizers that  issue
                        scsi  commands  with  an explicit timeout, in seconds; default taken from
                        /sys/block/sd<x>/device/timeout

       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. 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 300 if fast_io_fail_tmo is not set.

       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  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 no , avoids this problem. Default is yes

       bindings_file    The  full  pathname  of  the  binding  file   to   be   used   when   the
                        user_friendly_names option is set. Defaults to /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.  Defaults to /etc/multipath/wwids

       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

       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. 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 automatically use the alua  prioritizer.  If  not,
                        the prioritizer will be selected as usual. Default is no

       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

       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. Default is no

       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. Default
                        is /etc/multipath/conf.d

       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. 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. 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 In these cases it is
                        recommended to increase the  CLI  timeout  to  avoid  those  issues.  The
                        default is 1000

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.

       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,
       ie 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:

       wwid             The World Wide Identification of a device.

       property         Regular  expression  of  the udev property to be whitelisted. Defaults to
                        (ID_WWN|SCSI_IDENT_.*)

       devnode          Regular expression of the device nodes to be whitelisted.

       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             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 or devices section:

              path_grouping_policy
              path_selector
              prio
              prio_args
              failback
              rr_weight
              flush_on_last_del
              no_path_retry
              rr_min_io
              rr_min_io_rq
              features
              reservation_key
              deferred_remove
              delay_watch_checks
              delay_wait_checks

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         (Optional) Revision identfier

       product_blacklist
                        (Optional) Product strings to blacklist for this vendor

       alias_prefix     (Optional)  The  user_friendly_names  prefix to use for this device type,
                        instead of the default "mpath"

       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 rdac      Hardware handler for LSI/Engenio/NetApp E-Series RDAC storage
                                    controller.

                        1 hp_sw     Hardware   handler   for   Compaq/HP   storage   arrays    in
                                    active/standby mode.

                        1 alua      Hardware handler for SCSI-3 ALUA compatible arrays.

       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
              deferred_remove
              delay_watch_checks
              delay_wait_checks

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
              deferred_remove
              delay_watch_checks
              delay_wait_checks

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  was  developed  by  Christophe  Varoqui,  <christophe.varoqui@opensvc.com>  and
       others.

                                         30 November 2006                       MULTIPATH.CONF(5)