During the keynote session at NetApp Insight Berlin 2017, Octavian Tanase, Senior VP OSSG, announced to a cheering audience that “the next iteration of MetroCluster innovation,” MetroCluster™ IP, is available in NetApp® ONTAP® 9.3. MetroCluster IP brings business continuity to all data centers with no specialized gear to manage.

 

MetroCluster has a proven track record of enabling continuous availability of workloads for some of our largest enterprise customers. MetroCluster IP offers an alternative to the Fibre Channel fabric for back-end connectivity while retaining the same levels of reliability, scalability, simplicity, and performance. It enables 10% to 15% savings on capex and opex, while also simplifying both deployment and operations.

 

In ONTAP 9.3, MetroCluster IP is supported with the AFF A700 and FAS9000 in a 4-node configuration using the Nexus 3132Q switches that are a standard part of an ONTAP configuration. In this case, however, they serve not just the intracluster traffic but also the intercluster traffic between sites.

Characteristics of a MetroCluster IP configuration include:

  • Two 40G Ethernet switches per site
  • ONTAP nodes are connected directly to the storage shelf with SAS cables
  • The HA and intracluster traffic share the same switch with the intercluster traffic
  • Storage on each site is physically attached only to the local nodes
  • Remote storage is accessed by using optimized iSCSI with nodes acting as initiator and target
  • RDMA is through an iWARP card, one on each node, with two Ethernet ports

Why the new approach?

The new architecture uses the industry-standard TCP/IP protocol. In some areas of the world, Fibre Channel infrastructure is often more expensive to deploy, if even available.. Additionally, IP technologies have the advantage of less complex hardware requirements, because only network cards and switches are required. FC, on the other hand, requires specific interface cards and connectors.

 

MetroCluster IP provides a significantly improved configuration and operations experience, because there are no FC switches or FC-SAS bridges to configure and manage.

 

The MetroCluster simple commands to switch over and switch back remain in place, so the data center staff doesn’t have to learn new interactions during time-critical disaster operations.

Is MetroCluster IP managed differently?

There are some minor differences that administrators must consider in their operational workflows for MetroCluster IP. The storage on either side is attached only to the nodes on the same site. Although it is highly unlikely that both nodes on site A would fail at the same time, such a failure would require a switchover because the remote nodes would not be able to access the storage on site A. The role of a mediator (tie breaker) becomes more important in this case to facilitate an automated switchover during such a failure.

 

MetroCluster IP in ONTAP 9.3 provides most of the features available in MetroCluster FC, with these exceptions:

  • Available only with A700 and FAS9000 systems
  • Only 4-node fabric configuration is supported
  • Unmirrored aggregates are not supported

NOTE: MetroCluster FC configurations with A700 or FAS9000 currently deployed cannot be converted to MetroCluster IP, and existing ONTAP clusters based on these nodes cannot be upgraded to MetroCluster IP.

 

In ONTAP 9.3, specific requirements for network connectivity must be met. These restrictions will be relaxed in future ONTAP releases, so that the full value of MetroCluster IP can be realized.

  • The MetroCluster IP back end must use a dedicated physical link connecting the switches at the respective sites with stretched layer 2 connectivity. Ordering dedicated IP long-distance connectivity may be less expensive than dedicated FC connectivity.
  • NetApp recommends using a dual 40Gb link per switch for peak performance on an A700 MetroCluster IP configuration. If the workload does not require such a high throughput, 10Gb links can be used.
  • The distance between the two sites should be no more than 100km (60 miles).

Tune into this edition of the Tech ONTAP Podcast for more information about MetroCluster and our new IP support.

 

mm

Manish Thakur