About Data Replication

Data replication settings are accessible through the Core Management Console under the Replication menu, and through the coredr commands.

A single data center is susceptible to large-scale failures (power loss, natural disasters, hardware failures) that can bring down your network infrastructure. To mitigate such scenarios, product Replication enables you to connect branch offices to data centers across geographic boundaries and replicate data between them.

In a product setup, a typical storage area network (SAN) replication does not protect you from data loss in case of a data center failure, nor from network downtime that can affect many branch offices at the same time. FusionSync enables Cores in two geographically dispersed data centers to remain in synchronization and enables the Edges to switch to another Core in case of disaster. FusionSync can prevent data loss and downtime.

The product replication includes the following components:

• Primary Core—A role of Core that actively serves the LUNs to the Edges and replicates new writes to a secondary Core. During normal operations, the primary Core is located at the preferred data center. When a disaster, a failure, or maintenance affects the preferred data center, the primary Core fails over to the secondary Core at the disaster recovery site. After the failover, the secondary Core becomes primary.

• Secondary Core—A role of Core that receives replicated data from the primary Core. The secondary Core does not serve the storage LUNs to the Edges. On failover, the secondary Core changes its role to primary Core.

• Replication pair—A term used to describe the primary and secondary Core located in separate data centers and configured for FusionSync.

• Replica LUNs—LUNs at the secondary data center that are mapped to the secondary Core and kept in sync with the primary Core LUNs in the primary data center by using FusionSync.

• Journal LUN—A dedicated LUN that is mapped to the Cores from the local backend storage array. Each Core has its own Journal LUN. When FusionSync replication is suspended, the Core uses the Journal LUN to log the write operations from Edges.

• Witness—A role assigned to one of the Edges. A Witness registers requests to suspend replication from the Cores. A Witness makes sure that only one Core at a time suspends its replication. This suspended replication prevents a split-brain scenario and ensures the Edge’s write operations are logged to the Journal LUN on the Core approved by the witness.

You must meet the following requirements to set up replication:

• You must configure the backend storage array for each Core that is included in the replication configuration.

• The primary data center can reach the secondary data center through the chosen interfaces.

• Each replica LUN must be the same size (within 1 GiB) because its LUN counterpart is in the primary data center.

• The secondary Core must be either the same or larger specification model as the primary Core.

• If you have HA configured on the primary Cores of the data center, you must also configure it on the secondary Cores. The HA configuration must be the same in each case.