Long distance links for Metro Mirror and Global Mirror partnerships

The links between clustered system pairs that perform remote mirroring must meet specific configuration, latency, and distance requirements.

Figure 1 shows an example of a configuration that uses dual redundant fabrics that can be configured for Fibre Channel connections. Part of each fabric is located at the local system and the remote system. There is no direct connection between the two fabrics.

You can use Fibre Channel extenders or SAN routers to increase the distance between two systems. Fibre Channel extenders transmit Fibre Channel packets across long links without changing the contents of the packets. SAN routers provide virtual N_ports on two or more SANs to extend the scope of the SAN. The SAN router distributes the traffic from one virtual N_port to the other virtual N_port. The two Fibre Channel fabrics are independent of each other. Therefore, N_ports on each of the fabrics cannot directly log in to each other. See the following website for specific firmware levels and the latest supported hardware:


If you use Fibre Channel extenders or SAN routers, you must meet the following requirements:

Configuration requirements for systems that perform remote mirroring over extended distances (greater than 80 ms round-trip latency between sites)

If you use remote mirroring between systems with 80 - 250 ms round-trip latency, you must meet the following additional requirements:

In addition to the preceding list of requirements, the following guidelines are provided for optimizing performance for remote mirroring by using Global Mirror:

Limitations on host-to-system distances

There is no limit on the Fibre Channel optical distance between the system nodes and host servers. You can attach a server to an edge switch in a core-edge configuration with the system at the core. The system can support up to three ISL hops in the fabric. Therefore, the host server and the system can be separated by up to five Fibre Channel links. If you use longwave small form-factor pluggable (SFP) transceivers, four of the Fibre Channel links can be up to 10 km long.