Netapp Clustering

what is Cluster

A cluster is two storage systems (nodes) that are connected to each other either
directly or through switches. You can configure the two nodes so that they share
access to a single set of disks, subnets, and tape drives, or you can configure them
to have two distinct sets of storage, each owned by one of the nodes

What an active/active configuration


An active/active configuration is two storage systems (nodes) whose controllers are connected to each other either directly or, in the case of a fabric-attached MetroCluster, through switches and FC-VI interconnect adapters

You can configure the active/active configuration so that each node in the pair shares access to a commonset of storage, subnets, and tape drives, or each node can own its own distinct set of storage and subnets.

The nodes are connected to each other through a NVRAM adapter, or, in the case of systems with two controllers in a single chassis,

This allows one node to serve data that resides on the disks of its failed partner node.

Each node continually monitors its partner, mirroring the data for each other’s nonvolatile memory (NVRAM or NVMEM)

Benefits of Clustering:

Active/active configurations provide fault tolerance and the ability to perform nondisruptive upgrades and maintenance

• Fault tolerance
When one node fails or becomes impaired a takeover occurs, and the partner node continues to serve the failed node’s data.
the failed node’s data.
• Nondisruptive software upgrades
When you halt one node and allow takeover, the partner node continues to serve data for the halted node while you upgrade the node you halted.
• Nondisruptive hardware maintenance
When you halt one node and allow takeover, the partner node continues to serve data for the halted node while you replace or repair hardware in the node you halted

Characteristics of nodes in an active/active configuration

They are connected to each other either through a cluster interconnect consisting of adapters and cable, or, in systems with two controllers in the same chassis, through an internal interconnect. The nodes use the interconnect to do the following task.

• Continually check whether the other node is functioning
• Mirror log data for each other’s NVRAM
• Synchronize each other’s time

Each node manages its own disks or array LUNs
Each node in takeover mode manages its partner's disks or array LUNs
partner node takes over read/write access to the array LUNs owned by the failed node until
the failed node becomes available again.

deploying an active/active configuration


• Make sure that the controllers and disk shelves are on different power supplies or grids, so that a single power outage does not affect both components.
• Use VIFs (virtual interfaces) to provide redundancy and improve availability of network
communication

How Data ONTAP works with standard active/active configurations

Data ONTAP functions so that each node monitors the
functioning of its partner through a heartbeat signal sent between the nodes. Data from the NVRAM
of one node is mirrored by its partner, and each node can take over the partner's disks or array LUNs
if the partner fails. Also, the nodes synchronize each other’s time

Setup requirements for standard active/active configurations

Architecture compatibility
Both nodes must have the same system model and be running the same firmware version. See the
Data ONTAP Release Notes for the list of supported systems
Cluster interconnect adapters and cables must be installed, unless the system has two controllers in
the chassis and an internal interconnect.