IBM N Series - Storage Resource Management Issues

Chapter 7. Highly Available controller pairs 81
The back-end switches are configured with two independent and redundant Fibre Channel
switch fabrics. Each fabric can have a single or dual inter-switch link (ISL) connection that
operates at up to 8 Gbps. With a Fabric-attached MetroCluster, the distance between sites
can be expanded from 500 meters up to a maximum of 100 km.
Fabric-attached MetroClusters includes the following characteristics:
򐂰 Fabric-attached MetroClusters contain two complete, separate copies of the data volumes
or file systems that you configured as mirrored volumes or file systems in your HA pair.
򐂰 The fabric-attached MetroCluster nodes can be physically distant from each other beyond
the 500-meter limit of a Stretch MetroCluster.
򐂰 Maximum distance between the fabric-attached MetroCluster nodes is up to 100 km,
depending on the switch configuration.
򐂰 A fabric-attached MetroCluster connects the two controllers nodes and the disk shelves
through four SAN switches that are called the Back-end Switches.
򐂰 The Back-end Switches are IBM/Brocade Fibre Channel switches in a dual-fabric
configuration for redundancy.
Figure 7-5 shows a simplified Fabric-attached MetroCluster. Use a single disk shelf per Fibre
Channel switch port. Up to two shelves are allowed.
Figure 7-5 Simplified Fabric-attached MetroCluster
Setup requirements and restrictions for fabric-attached MetroClusters
You must follow certain requirements and restrictions when you are setting up a new
fabric-attached MetroCluster configuration.
The setup requirements for a fabric-attached MetroCluster include those for standard and
mirrored HA pairs, with the following exceptions.
Tip: The back-end Fibre Channel switches can be used for HA node pair and disk shelf
pair connectivity only.