Introduction to Nutanix cluster components

In this article I will briefly explain about the different components of a Nutanix cluster. The major components are listed below.

Nutanix cluster components

1. Stargate: Data I/O manager for the cluster.
2. Medusa: Access interface for Cassandra.
3. Cassandra: Distributed metadata store.
4. Curator: Handles Map Reduce cluster management and cleanup.
5. Zookeeper: Manages cluster configuration.
6. Zeus: Access interface for Zookeeper.
7. Prism: Management interface for Nutanix UI, nCLI and APIs.

Stargate

• Responsible for all data management and I/O operations.
• It is the main point of contact for a Nutanix cluster.
• Workflow: Read/ write from VM < > Hypervisor < > Stargate.
• Stargate works closely with Curator to ensure data is protected and optimized.
• It also depends on Medusa to gather metadata and Zeus to gather cluster configuration data.

Medusa

• Medusa is the Nutanix abstraction layer that sits infront of DB that holds the cluster metadata.
• Stargate and Curator communicates to Cassandra through Medusa.

Cassandra

• It is a distributed high performance and scalable DB.
• It stores all metadata about all VMs stored in a Nutanix datastore.
• It needs verification of atleast one other Cassandra node to commit its operations.
• Cassandra depends on Zeus for cluster configuration.

Curator

• Curator constantly access the environment and is responsible for managing and distributing data throughout the cluster.
• It does disk balancing and information life cycle management.
• It is elected by a Curator master node who manages the task and job delegation.
• Master node coordinates periodic scans of the metadata DB and identifies cleanup and optimization tasks tat Stargate or other components should perform.
• It is also responsible for analyzing the metadata, this is shared across all Curator nodes using a Map Reduce algorithm. 

Zookeeper

• It runs on 3 nodes in the cluster.
• It can be increased to 5 nodes of the cluster.
• Zookeeper coordinates and distributes services.
• One is elected as leader.
• All Zookeeper nodes can process reads.
• Leader is responsible for cluster configuration write requests and forwards to its peers.
• If leader fails to respond, a new leader is elected.

Zeus

• Zeus is the Nutanix library interface which all other components use to access cluster configuration information.
• It is responsible for cluster configuration and leadership logs.
• If Zeus goes down, all goes down!

Prism

• Prism is the central entity of viewing  activity inside the cluster.
• It is the management gateway for administrators to configure and monitor a Nutanix cluster.
• It also elects a node.
• Prism depends on data stored in Zookeeper and Cassandra.

Note: All the info provided above are based on Nutanix 4.5 Platform Professional (NPP) administration course.