Knowledge Base

Why should I use persistent binding on my EMC® storage array?

For a fabric configuration, EMC highly recommends enabling persistent binding. Without a persistent binding mechanism, the host will be unable to maintain a persistent logical routing of communication from a storage device object across the fabric to an EMC storage array volume. If the physical configuration of the switch is changed (for example, cables are swapped or the host is rebooted), the logical route becomes inconsistent. This could cause possible data corruption.

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Modify the options lpfcdd line in the /etc/modules.conf file to set persistent binding.

1. At the command type cd /proc/scsi/lpfc and press the <Enter> key.
   The command context will be changed to /proc/scsi/lpfc.
2. Type grep WWPN* at the command prompt and press the <Enter> key.
   The initiator and target information output should be similar to the following:
   
   1: lpfc0t00 DID 010a00 WWPN 50:06:01:60:00:60:00:ed WWNN 50:06:01:60:00:60:00:ed
   1: lpfc0t01 DID 011700 WWPN 50:06:01:69:00:60:00:ed WWNN 50:06:01:60:00:60:00:ed
   2: lpfc1t00 DID 010a00 WWPN 50:06:01:61:00:60:00:ed WWNN 50:06:01:60:00:60:00:ed
   2: lpfc1t01 DID 011700 WWPN 50:06:01:68:00:60:00:ed WWNN 50:06:01:60:00:60:00:ed
   
   

   NOTE:

   In the example above :lpfcxt0x is the initiator and 50:06:01:6x:00:60:00:ed following WWPN is the Target WWPN. The number of bind entries in this example is 4.

   
   
3. Use a text editor to open the /etc/modules.conf file.
4. Add the following entries to the end of the options lpfcdd line.
   
   

   NOTE:

   The following entries should be entered as one line, they have been split up below for carity. The Target WWPN should have the colons removed. There should be a Target WWPN:initiator entry for each of the bind entries.

   
   lpfc_lun_skip=1
   lpfc_bind_entries=x Where x is number of bind entries, 4 in the example above.
   lpfc_scandown=0
   lpfc_automap=0
   lpfc_fcp_bind_WWPN=Target WWPN:initiator,Target WWPN:initiator,Target WWPN:initiator,Target WWPN:initiator
   Where Target WWPN is the Target WWPN with the colons and any spaces removed, and initiator is the initiator, both of these are obtained from step 2.
   
   The completed line should look similar to this:
   
   options lpfcdd lpfc0_topology=0x02 lpfc1_topology=0x02 lpfc_network_on=0 lpfc_use_data_direction=0 lpfc_lun_skip=1 lpfc_bind_entries=4 lpfc_scandown=0 lpfc_automap=0 lpfc_fcp_bind_WWPN=50060160006000ed : lpfc0t00 ,50060169006000ed : lpfc0t01 ,50060161006000ed : lpfc1t00 ,50060168006000ed : lpfc1t01
   
5. Confirm a line similar to the example below exists, if it does not add it to the file.
   
   options scsi_mod max_scsi_luns=256 scsi_allow_ghost_devices=1
   
6. Save the chages made to /etc/modules.conf and close the text editor.
7. Make a new initial ram disk by typing mkinitrd at the command prompt and pressing <Enter>.
8. Reboot the server by typing reboot at the command line and pressing <Enter>.
   Persistent binding is now set on the array.

NOTE:

The persistence information should only be updated if there is a change to the WWPN that the host sees or the initiator identifier on the host.

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