Recommended stretch MetroCluster configuration with array LUNs

When configuring a stretch MetroCluster configuration with Data ONTAP systems and storage arrays, you should follow the best practice recommendations for how to connect the hardware components. The Interoperability Matrix at support.netapp.com contains information about the hardware components that are supported for a MetroCluster configuration using array LUNs.

The following illustration shows the components and best practice for a stretch MetroCluster configuration with storage arrays.

Note: FC initiator port names on Data ONTAP systems differ between some platforms. Your platform's port names might not match the port names shown in the illustration. The Hardware Universe contains information that helps you determine in which slot to install the FC-VI adapter for your platform.
This graphic is described by the surrounding text.

Interconnections on Data ONTAP systems

In a stretch MetroCluster configuration, the Data ONTAP systems are connected directly.

The sample illustration shows the connections between a dual-enclosure HA pair for systems that can contain only one controller in the enclosure.

For Data ONTAP systems that are dual-enclosure systems with two controllers in the same chassis, such as 31xx systems, you install a Data ONTAP system at each site. To implement the stretch MetroCluster configuration, you must install an FC-VI adapter in each controller to provide the HA interconnect between the systems.

Note: When the FC-VI adapter is installed in the system, the internal InfiniBand interconnect is automatically disabled.

The following illustration shows the FC-VI port connections between HA pair systems such as the 31xx. Each enclosure contains two controllers. You configure two separate MetroCluster configurations among the four controllers.

In the stretch MetroCluster illustration, one MetroCluster configuration is between Controller A and Controller C.

From Controller A To Controller C
FC-VI port A FC-VI port A
FC-VI port B FC-VI port B

In the stretch MetroCluster illustration, the other MetroCluster configuration is between Controller B and Controller D.

From Controller B To Controller D
FC-VI port A FC-VI port A
FC-VI port B FC-VI port B

Some older V-Series models use NVRAM to connect the systems in a MetroCluster configuration. The following table lists the NVRAM connections on V-Series systems that connect to each other through NVRAM.

vs1 vs2
NVRAM port L02 Ph2 NVRAM port L02 Ph2
NVRAM port L01 Ph1 NVRAM port L01 Ph1

Inter-Switch Link connections (ISLs)

Stretch MetroCluster configurations use a switched fabric to connect the local half of the configuration to the remote half of the configuration. In the stretch MetroCluster illustration, Switches 1 and 3 are connected to each other (Fabric 1). Switches 2 and 4 are also connected (Fabric 2).

  • The first fabric in the MetroCluster configuration begins from Switch 1 on Site A (local) and is completed by connecting the ISL cable to the first switch on Site B (remote)—Switch 3.
  • The second fabric is created using Switch 2 on Site A (local), connected through a second ISL cable to the second switch on Site B (remote)—Switch 4.
ISL connection Switch Fabric
Port 4 on switch 1 Port 8 on switch 3 Fabric 1
Port 11 on switch 2 Port 15 on switch 4 Fabric 2

Data ONTAP system-to-switch connections

The best practice connections in the stretch MetroCluster with storage arrays illustration eliminate a single-point-of-failure in the following ways:

  • FC initiator ports on the same FC controller chip (for example, port 0a and 0b) connect to alternate fabrics.
  • Multiple paths and zones ensure that FC initiator ports on the same controller chips access the array LUN from different Data ONTAP systems and switch fabrics.

The following table lists the connections from the Data ONTAP system to the switch:

Data ONTAP system and FC initiator port Switch
vs1: FC port 0a Switch 1: Port 1
vs1: FC port 0b Switch 2: Port 9
vs1: FC port 0c Switch 1: Port 2
vs1: FC port 0d Switch 2: Port 10
vs2: FC port 0a Switch 3: Port 5
vs2: FC port 0b Switch 4: Port 13
vs2: FC port 0c Switch 3: Port 6
vs2: FC port 0d Switch 4: Port 14

Storage array-to-switch connections

The best practice connections from the storage array to the switch are as follows:

  • Ports 1A and 2A on each storage array connect to alternate fabrics.
  • Ports 1B and 2B on each storage array connect to alternate fabrics.
  • Data ONTAP systems are configured to access any array LUN on two storage array paths (1A and 2A or 1B and 2B).
Storage array port Switch Fabric
Array 1: Port 1A Switch 1: Port 3 1
Array 1: Port 2A Switch 2: Port 12 2
Array 1: Port 1B Switch 1: Port 5 1
Array 1: Port 2B Switch 2: Port 13 2
Array 2: Port 1A Switch 3: Port 7 1
Array 2: Port 2A Switch 4: Port 16 2
Array 2: Port 1B Switch 3: Port 9 1
Array 2: Port 2B Switch 4: Port 17 2