multipathing configuration

  vi /etc/multipath.conf
   modprobe dm-multipath
 service multipathd start
  multipath -d
   vi /etc/multipath.conf
   multipath -d
   multipath -v2
   multipath -ll

 How to find WWID numbers to add in below file
 [root@GPFS1 ~]# for A in `fdisk -l 2>/dev/null | egrep '^Disk' | grep bytes | cut -d " " -f2|cut -d ":" -f1 `;do echo $A;/lib/udev/scsi_id --page=0x83 --whitelisted --device=$A;done
/dev/sda
3600605b001cfb94019816f7425cd9f1f
/dev/mapper/VolGroup-lv_root
/dev/mapper/VolGroup-lv_swap
/dev/mapper/VolGroup-lv_home
/dev/sdf
3600a0b80006e1d2e0000aa4c51f5d1b1
/dev/sdc
3600a0b80006e1d2e0000efc05010cb10
/dev/sde
3600a0b80006e1d2e000095d751ecc295
/dev/sdg
3600a0b80006e1d2e0000efc95010cb62
/dev/sdh
3600a0b80006e1d2e0000b09e51fa2371
/dev/sdj
3600a0b80006e1992000067475010ca33
/dev/sdo
3600a0b80006e1d2e0000efc05010cb10
/dev/sdq
3600a0b80006e1d2e000095d751ecc295
/dev/sdr
3600a0b80006e1d2e0000aa4c51f5d1b1
/dev/sds
3600a0b80006e1d2e0000efc95010cb62
/dev/sdt




 vi /etc/multipath.conf
 [root@GPFS1 ~]# cat /etc/multipath.conf
# This is a basic configuration file with some examples, for device mapper
# multipath.
# For a complete list of the default configuration values, see
# /usr/share/doc/device-mapper-multipath-0.4.9/multipath.conf.defaults
# For a list of configuration options with descriptions, see
# /usr/share/doc/device-mapper-multipath-0.4.9/multipath.conf.annotated
#
# REMEMBER: After updating multipath.conf, you must run
#
# service multipathd reload
#
# for the changes to take effect in multipathd

## By default, devices with vendor = "IBM" and product = "S/390.*" are
## blacklisted. To enable mulitpathing on these devies, uncomment the
## following lines.
#blacklist_exceptions {
#       device {
#               vendor  "IBM"
#               product "S/390.*"
#       }
#}

## Use user friendly names, instead of using WWIDs as names.
defaults {
        user_friendly_names yes
}
##
## Here is an example of how to configure some standard options.
##
#
#defaults {
#       udev_dir                /dev
#       polling_interval        10
#       path_selector           "round-robin 0"
#       path_grouping_policy    multibus
#       getuid_callout          "/lib/udev/scsi_id --whitelisted --device=/dev/%n"
#       prio                    alua
#       path_checker            readsector0
#       rr_min_io               100
#       max_fds                 8192
#       rr_weight               priorities
#       failback                immediate
#       no_path_retry           fail
#       user_friendly_names     yes
#}
##
## The wwid line in the following blacklist section is shown as an example
## of how to blacklist devices by wwid.  The 2 devnode lines are the
## compiled in default blacklist. If you want to blacklist entire types
## of devices, such as all scsi devices, you should use a devnode line.
## However, if you want to blacklist specific devices, you should use
## a wwid line.  Since there is no guarantee that a specific device will
## not change names on reboot (from /dev/sda to /dev/sdb for example)
## devnode lines are not recommended for blacklisting specific devices.
##
blacklist {
#       wwid 26353900f02796769
        devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
        devnode "^hd[a-z]"
}
#multipaths {
#       multipath {
#               wwid                    3600508b4000156d700012000000b0000
#               alias                   yellow
#               path_grouping_policy    multibus
#               path_checker            readsector0
#               path_selector           "round-robin 0"
#               failback                manual
#               rr_weight               priorities
#               no_path_retry           5
#       }
#       multipath {
#               wwid                    1DEC_____321816758474
#               alias                   red
#       }
#}
#devices {
#       device {
#               vendor                  "COMPAQ  "
#               product                 "HSV110 (C)COMPAQ"
#               path_grouping_policy    multibus
#               getuid_callout          "/lib/udev/scsi_id --whitelisted --device=/dev/%n"
#               path_checker            readsector0
#               path_selector           "round-robin 0"
#               hardware_handler        "0"
#               failback                15
#               rr_weight               priorities
#               no_path_retry           queue
#       }
#       device {
#               vendor                  "COMPAQ  "
#               product                 "MSA1000         "
#               path_grouping_policy    multibus
#       }
#}
blacklist_exceptions {
        wwid "3600a0b80006e1d2e0000aa4c51f5d1b1"
        wwid "3600a0b80006e1d2e0000efc05010cb10"
        wwid "3600a0b80006e1d2e000095d751ecc295"
        wwid "3600a0b80006e1d2e0000efc95010cb62"
        wwid "3600a0b80006e1d2e0000b09e51fa2371"
        wwid "3600a0b80006e1992000067475010ca33"
}
multipaths {
  multipath {
      wwid "3600a0b80006e1d2e0000aa4c51f5d1b1"
      alias mpath0
  }
  multipath {
      wwid "3600a0b80006e1d2e0000efc05010cb10"
      alias mpath1
  }
  multipath {
      wwid "3600a0b80006e1d2e000095d751ecc295"
      alias mpath2
  }
  multipath {
      wwid "3600a0b80006e1d2e0000efc95010cb62"
      alias mpath3
  }
  multipath {
      wwid "3600a0b80006e1d2e0000b09e51fa2371"
      alias mpath4
  }
  multipath {
      wwid "3600a0b80006e1992000067475010ca33"
      alias mpath4
  }

}
#blacklist {
#       devnode "*"
#}
[root@GPFS1 ~]#


   modprobe dm-multipath
 service multipathd start
   multipath -d
   multipath -v2
   multipath -ll