Dell Unity: How to Ensure that Async Block Replication Uses Multiple Network Interfaces

Summary: Unity may assign the same replication interface pair to every session when creating LUN replication sessions. The best way to ensure this does not happen is to manually create the replication sessions using UEMCLI. (User Correctable) ...

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Instructions

To ensure that multiple replication interfaces are being used: 

  1. Create two LUNs with identical settings on the source and destination (do not configure replication yet).
  2. Create the replication interfaces intended for use.

Steps 1 and 2 are done using the Unisphere UI.

  1. Set the replDest flag to yes on the destination side.
Here is the command syntax: 
uemcli -u Local/admin -p Password123456789 /stor/prov/luns/lun -id sv_2 set -replDest yes
  1. Create the replication session using uemcli.
Here is a working syntax example. This is done on a VSA. On a hardware system, Specify replication interfaces for SPB as well: 
uemcli -u Local/admin -p Password123456789 /prot/rep/session create -name REP1 -srcRes sv_2 -srcSPAInterface if_6 -dstType remote -dstSys RS_1 -dstSPAInterface if_5 -dstRes sv_2 -syncType auto -rpo 60m


The identifiers required for the command inputs are found in Unisphere by enabling the CLI ID column for the relevant item type.

Once all the wanted replication interfaces are created, use an uemcli command such as the following to validate that the sessions are using the correct layer three interfaces:

$ uemcli /prot/rep/session show -filter "Name,ID,Source resource,Source SP-A interface,Source SP-B interface,Destination resource,Destination SP-A interface,Destination SP-B interface"
Storage system address: 127.0.0.1
Storage system port: 443
HTTPS connection

1:    Name                       = REP1
      ID                         = 42949672969_VIRT2213XBSFIV_0000_42949672967_VIRT1615KVBVLJ_0000
      Source resource            = sv_1
      Source SP-A interface      = 5.6.7.90
      Source SP-B interface      = N/A
      Destination resource       = sv_2
      Destination SP-A interface = 5.6.7.94
      Destination SP-B interface = N/A

2:    Name                       = REP2
      ID                         = 42949672970_VIRT2213XBSFIV_0000_42949672974_VIRT1615KVBVLJ_0000
      Source resource            = sv_2
      Source SP-A interface      = 5.6.7.91
      Source SP-B interface      = N/A
      Destination resource       = sv_3
      Destination SP-A interface = 5.6.7.95
      Destination SP-B interface = N/A

3:    Name                       = REP3
      ID                         = 42949672971_VIRT2213XBSFIV_0000_42949672975_VIRT1615KVBVLJ_0000
      Source resource            = sv_3
      Source SP-A interface      = 5.6.7.92
      Source SP-B interface      = N/A
      Destination resource       = sv_4
      Destination SP-A interface = 5.6.7.96
      Destination SP-B interface = N/A

4:    Name                       = REP4
      ID                         = 42949672972_VIRT2213XBSFIV_0000_42949672976_VIRT1615KVBVLJ_0000
      Source resource            = sv_4
      Source SP-A interface      = 5.6.7.93
      Source SP-B interface      = N/A
      Destination resource       = sv_5
      Destination SP-A interface = 5.6.7.97
      Destination SP-B interface = N/A

If using LACP for async replication, also adjust the xmit_hash_policy to layer 3+4 (policy #1) to allow the system to transmit traffic for different IPs across different interfaces.

Additional Information

See the related article Dell Unity: How to change LACP trunk or bond load-balancing algorithm (Dell Correctable)

Affected Products

Dell EMC Unity, Dell EMC Unity Family
Article Properties
Article Number: 000211847
Article Type: How To
Last Modified: 28 May 2025
Version:  5
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