Dell PowerStore Protecting Your Data

• When a synchronous replication session is created, a matching read-only resource is created on the destination system. A read-only definition of the protection policy is also created on the destination system. This policy is used if the replication session is failed over.
• User snapshots:
  • Snapshots of the resource that were created before the session was created are synchronized to the destination system.
  • After the replication session is created, user snapshots are performed simultaneously on the source and destination systems with near identical content.
  • User snapshots that are created when the replication session is paused are not replicated to the destination system after resume or recovery.
• To change the parameters of a resource (such as name, size, and performance policy), you must pause the replication session.
• You can switch from synchronous to asynchronous replication by modifying the replication rule in the assigned protection policy.

During synchronous block replication, you can perform the following :

• Intracluster migration - During cut-over, the replication session state changes to Paused for Migration. The replication session resumes its state when migration is completed. Sessions that were paused when migration started remain paused.
• NDU - Replication sessions which have an Operating Normally status when NDU starts, continue to be active during NDU. Paused replication sessions status changes to Paused for NDU.
• Cluster reconfiguration - You can reconfigure the cluster replication network, expand or scale down the cluster, or relocate the cluster. Replication resumes after the reconfiguration is complete.

When a volume on the destination system is mapped to a host, the system sets the node affinity for this volume, and as a result, all I/Os are automatically directed to the selected node. You do not have to pause and resume the replication session for the I/O redirection to take effect. Setting node affinity for volumes on the destination system provides load balancing and prevents latency of replication. You can set the node affinity manually using REST API.

The following applies for volume group synchronous replication:

• All members must reside on the same appliance.
• Only volume groups with configured write-order consistency can be assigned with a protection policy with a synchronous replication rule.
• A protection policy that is assigned to a volume group applies to all members of the group. Individual volumes in a volume group cannot be protected by a protection policy.
• To change the parameters of a volume group (such as name, performance policy, and write-order consistency), you must pause the replication session that is assigned to it.