•    This KBA refers to Dell EMC Unity asynchronous replication only.
•    This KBA substitutes Legacy Article KBA 327281

   Celerra - How to properly modify interfaces for Replicator V2 operations
 

•    The following is a supplement to the official replication documentation found here:

 https://support.emc.com/docu69886_Unity:-Replication-Technologies---A-Detailed-Review.pdf?language=en_US
 http://www.emc.com/dam/uwaem/documentation/unity-p-replication-config.pdf  

   Assumptions :
  
   1. Customer is replicating over LAN between two Dell EMC Unity's , intends to perform a network configuration change or otherwise ship the destination, upon full sync-completion, to a disaster recovery site where a different network configuration would need to be in place.

   2. Alternatively , Customer might have an unexpected power outage and wishes to bring the DR system online but re-establish sync to original source after a network configuration change
   
   3.  Replication state would be 'Lost Synchronization ' in Unisphere following a power down.

  ---------------------------------------------------------------------------------------------------------------------------------------------

   Dell/EMC Recommendations for Pre work :

      1. Create new network interfaces on both source and target beforehand and perform a ping test if possible.
           If the system is going to the DR , that may not be possible. at the very least perform a network planning and ensure designated ip address are going to be able to route between the new source and destination ip's
   
      2.  Following a full sync and just before shutting down , issue pause to all replication sessions.
           This simple step would help ensure that replication changes can complete  after a system is powered back up.

      3.  Performing a reconfiguration of network  following Dell EMC Unity power up on remote site would also require the verification of the connection before replication can be restarted [verify and update task in Unisphere] :

• Customer must add new ip interface and not try to modify existing (this would be allowed when replication is paused but would cause Unisphere to CLI break-mismatch that in turn would impact the start operation).
• Optionally if actually required, add new IPs on the original source as well.
• Use CLI interface on both platforms to perform connectivity checks :

           spa$ ping -I eth2 "DST IP"  ==> can use actual SRC IP ADDR in the interface argument.
           Similarly traceroute tool can be used with :  -i device  --interface=device
           Note - These tools exist on Dell EMC Unity settings - route
                      (but only if iscsi interface was setup see KBA 492286 for more info)

•     If network connection is achieved, customer must "verify and update" the replication connection next.  

               This task is actually going to fail as the old IP's are still there, however it will show the new IPs updated after the task failure, from within the connection properties. Ignore Task failure , verify connection properties is ok.

      4.   Every Replication Session has its own associated ip addresses configuraton.
            Dell EMC Unity Unisphere Replication-sessions-properties page however does not include that associated IP information ,

            As a result , replication sessions must be modified using UEMCLI only :
        
             service@(none) spb:~> uemcli /prot/rep/session -h

4.1 Unity OE or Older :

  [Set]
  /prot/rep/session { -id <value> | -name <value> } set [ -paused { yes | no [ -forceFullCopy ] } ] [ -newName <value> ] [ -srcSPAInterface <value> ] [ -dstSPAInterface <value> ] [ -srcSPBInterface <value> ] [ -dstSPBInterface <value> ] [ -syncType { manual | auto -rpo <value> } ]


Newer Uemcli Unity OE :

please review the following notes carefully:

1. User must use admin account for any configuration change including pause and resume commands.
2. User must initiate all pause operations with the filesystems first , followed by the VDM.
3. The source and destination IP address should be entered as "interface id"
    (for example : -srcSPAInterface if_27 -dstSPAInterface if_33 -srcSPBInterface if_26 -dstSPBInterface if_34)

  [Pause]
  /prot/rep/session { -id <value> | -name <value> } pause [ -async ]

  [Resume]
  /prot/rep/session { -id <value> | -name <value> } resume [ -async ] [ -forceFullCopy ] [ -srcSPAInterface <value> ] [ -dstSPAInterface <value> ] [ -srcSPBInterface <value> ] [ -dstSPBInterface <value> ]


      5. Once Replication session information is updated , The umecli command is also going to start it (-paused no) , so confirm replication is progressing using Unipshere session page or uemcli /prot/rep/session show
Once confirmed , you can go to Unisphere Interface page and issue a delete too the older IPs.
Once removed,  execute verify and update from the connection page and confirm it is validating without further failures.
  
      6. Monitor replication as needed on the new network (bandwidth) and confirm all is going in sync properly
          (bandwidth will be divided equally between the various active session so determine the total bandwidth based on total.
      
          
  

    


   
  
  

 

•      This procedure is in place in order to warn customer beforehand , that shutting down the target system before issuing a Pause would cause "lost synchronization' state , and at current code this state may be unrecoverable - requiring deletion and full sync.
• Before applying this KB, please make sure the connection "verify and update" successfully. If connection "verify and update" failed, any modify or update connection will fail.

• Please also refer to KB(504733) to make sure the TCP ports ( 443,5085,8888) required for replication are open on both source and destination sides.

•  This guide is also for Tech Support Engineers to assist customer with proper planning as well as actual execution in case of issues.
• Future Dell EMC Unity codes are going to introduce 'out of sync' common-base replication restart.