This section describes how to configure high availability for Core-enabled Edges. Edge high availability enables you to configure two Edge appliances so that either one can fail without disrupting the service of any of the LUNs provided by the Core.

To enable Edge high availability, you configure a pair of Edges: one as an active peer and the other as a standby peer. The active Edge in the pair connects to the Core and serves storage data. The active peer contains the authoritative copy of the blockstore and configuration data. The standby Edge is passive and does not service client requests but is ready to take over from the active peer immediately.

As the system writes new data to the active peer, it reflects the data to the standby peer, which stores a copy of the data in its local blockstore. The two appliances maintain a heartbeat protocol between them, so that if the active peer goes down, the standby peer can take over servicing the LUNs. If the standby peer goes down, the active peer continues servicing the LUNs, after raising a high-availability alarm indicating that the system is now in a degraded state.

After a failed peer resumes, it resynchronizes with the other peer in the HA pair to receive any data that was written since the time of the failure. When the peer catches up by receiving all the written data, the system resumes Edge high availability, reflects future writes to both peers, and clears the alarm.

When you configure Edge high availability, we recommend setting up Edge multipath I/O (MPIO). This ensures that a failure of any single component (such as a network interface card, switch, or cable) does not result in a communication problem between the between the iSCSI initiators and the Edge.