Fabric Attached MetroCluster

What a Fabric Attached MetroCluster is

A Fabric Attached MetroCluster is a clustered system where the local and partner nodes are separated by more than 500 meters and up to 30 kilometers. Each node and associated disk shelves are connected directly to a pair of Fibre Channel switches, then across some distance, to the partner node and disk shelves. Disk shelf and node ownership are determined by where they are plugged into the switch and combined with the partner switch, create a fabric.

What a switch fabric is

A Fabric Attached MetroCluster contains two fabrics. A switch fabric consists of one switch connected to a switch on the partner half of the cluster. The two switches are connected to each other through the long distance ISL cables.

For example, the first fabric in a MetroCluster begins from Switch 1 and is completed by connecting the ISL to the first switch on the partner side--Switch 3. The second fabric consists of the second switch, connected through a second ISL cable, to the second switch on the partner side--Switch 4.

How switches are divided

The Fibre Channel switches are divided into banks and quadrants. Each switch has two banks and four quadrants, dividing the switch into equal parts. For example, a Brocade 3800 switch has 16 ports, divided into two banks of eight ports per bank.

The banks are further subdivided into two quadrants of four ports each (two for the Brocade 3200). These quadrants are also identified as Pools, which function the same in a Fabric Attached MetroCluster as in a mirrored cluster disk pool. Quadrants 1 and 3 belong to Pool 0, while quadrants 2 and 4 belong to Pool 1. Each switch bank contains a Pool 0 and Pool 1.

See the Data Protection Guide for a detailed discussion of disk pools.

The following illustration shows a Brocade 3800 switch, divided into banks, quadrants, and pools.

How disk ownership is determined

Disk ownership by a node is determined by where the FC HBA for Disk connects into the switch and by where the disks connect to the switch banks. FC HBAs connect to one switch bank, and own the disks on the other switch bank. For example, if the local node has its FC HBA adapters connect to Bank 1, it owns the disks connected to Bank 2.

Advantages of Fabric Attached MetroClusters

The advantages of Fabric Attached MetroClusters are the same as those of standard or mirrored clusters. See Standard clusters and Mirrored clusters and MetroClusters for information about the advantages of each cluster type.

In addition, Fabric Attached MetroClusters have the following advantages:

Expanded distance between halves of the cluster beyond 500 meters.
Disk shelves and nodes are not connected directly to each other, but are connected to a fabric, with multiple data routes.

How Data ONTAP works with these MetroClusters

Data ONTAP functions the same as it does in a nonswitched MetroCluster.

Setup requirements and restrictions

Cabling a Fabric Attached MetroCluster is the same as for standard or mirrored clusters, with the following exceptions:

Each clustered pair of nodes must use two switches, per cluster side, to communicate with the clients.
Switches must be either Brocade 3200 or 3800 and must be the same type on each side of the MetroCluster.
Each node must have the HBA kit installed and running.
Each node must have the VI-MC cluster adapter installed; slot position is dependent on the type of filer.
syncmirror_local and cluster_remote must be licensed and enabled on the local and partner nodes.
Mixed switch types can be used, but must be the same type on each side of the cluster.