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===== No multipath devices found =====
==== Error description ====
As stated [[public:iscsi:multipath|here]] multipath hardly causes trouble. But a case was observed, where the command ''multipath -l'' did not display any multipath devices although the host was properly logged into iSCSI LUNs:
  root@kvm55:~# iscsiadm -m session
  tcp: [1] 10.48.2.11:3260,582 iqn.2000-05.com.3pardata:25820002ac002071
  tcp: [2] 10.48.2.10:3260,482 iqn.2000-05.com.3pardata:24820002ac002071  
  root@kvm55:~# multipath -l
  root@kvm55:~#
==== Failure cause ====
The configuration of the running multipath service contained two definitions of the used multipath device:
  root@kvm55:~# multipathd show config | grep -B 1 -A 10 3PAR
  device {
	  vendor "3PARdata"
	  product "VV"
    ...
	  prio const
  }
  device {
	  vendor "3PARdata"
	  product "VV"
    ...
	  prio const
  }
The two definitions of the same device are clearly seen. The definition content was abbreviated in the picture above.

The configuration of the running multipath service always consists of the default configuration and the settings from the configuration file '/etc/multipath.conf'. Thus one device definition was delivered by the default configuration, the other one was read from the local configuration file '/etc/multipath.conf'.
==== Solution ====
Deleting the device definition from the configuration file (not depicted) and restarting multipath solved the problem:
  root@kvm55:~# service multipath-tools restart
   * Stopping multipath daemon multipathd                                 [ OK ]
   * Starting multipath daemon multipathd                                 [ OK ]
  root@kvm55:~# multipath -l
  350002ac21d622071 dm-4 3PARdata,VV
  size=5.0G features='0' hwhandler='0' wp=rw
  `-+- policy='round-robin 0' prio=-1 status=active
    |- 6:0:0:0 sdb 8:16 active undef running
    `- 5:0:0:0 sdc 8:32 active undef running
  350002ac21d632071 dm-2 3PARdata,VV
  size=500G features='0' hwhandler='0' wp=rw
  `-+- policy='round-robin 0' prio=-1 status=active
    |- 6:0:0:1 sdd 8:48 active undef running
    `- 5:0:0:1 sde 8:64 active undef running
=== Background information ===
The error occurred after a host restart. Probably a multipath update added the device description to the multipath default configuration. The 2nd device definition was then found at next multipath restart.

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