Dell PowerVault ME5 Series Administrator's Guide

Peer connections

A peer connection enables bi-directional communication between a local system and a remote system to transfer data between the two systems. Creating a peer connection requires a name for the peer connection and either an IP address of a single available iSCSI host port on the remote system, or a WWN of a single available FC host port on the remote system. Only iSCSI and FC host ports are used for the peer connection. Establishing a peer connection for virtual storage is required for replication. SAS host ports do not support peer connections

The peer connection is defined by the ports that connect the two peer systems, as well as the name of the peer connection. The local system uses the remote address to internally run the query peer-connection CLI command. The results of the query are used to configure the peer connection.

The prerequisites to create a peer connection are:

• Both systems must have iSCSI or FC host ports. Ports at both ends of the connection must use the same protocol.
• Both systems must be connected to the same fabric or network via a switch; direct connection between storage systems is not supported.
• All host port addresses in both systems must be unique, even for ports not in use.
• If iSCSI CHAP is configured for the peer connection, the authentication must be valid.

You can create a maximum of four peer connections per storage system. However, only one peer connection is allowed to a particular remote system. Attempting to create a second peer connection to the same system will fail. While creating the peer connection, the local system receives information about all host ports on the remote system as well as the port health on remote systems. It also links host ports of the selected host port type on the local system to those reachable on the remote system, so all ports of that type are available as part of the peer connection. Once created, the peer connection exists on both the local and remote systems.

Replications use a bi-directional communication path between the systems when exchanging information and transferring replicated data. Because the peer connection is bi-directional, replication sets can be created from both systems with replication occurring from either direction. Due to the relationship between peer connections and replication sets, creating a peer connection is part of the process of creating a replication set.

To create a peer connection, create a replication set Provisioning > Volumes > Data Protection > Add Data Protection > Remote Replication. Select one or more volumes to add to the replication set, then follow the on-screen directions to establish a peer connection between the primary and secondary systems. Directions include steps to enter the port address for the secondary system, the connection name, and the username and password of a user with a manage role on the remote system.

If a single host port loses connectivity, event 112 will be logged. Because a peer connection is likely to be associated with multiple host ports, the loss of a single host port may degrade performance but usually will not cause the peer connection to be inaccessible.