How can you define a cluster and what are its basic types?
A cluster is two or more computers (called nodes or members) that work together to perform a task. There are four major types of clusters:
  • Storage
  • High availability
  • Load balancing
  • High performance

What is Storage Cluster?
  • Storage clusters provide a consistent file system image across servers in a cluster, allowing the servers to simultaneously read and write to a single shared file system. 
  • A storage cluster simplifies storage administration by limiting the installation and patching of applications to one file system. 
  • The High Availability Add-On provides storage clustering in conjunction with Red Hat GFS2
What is High Availability Cluster?
  • High availability clusters provide highly available services by eliminating single points of failure and by failing over services from one cluster node to another in case a node becomes inoperative. 
  • Typically, services in a high availability cluster read and write data (via read-write mounted file systems). 
  • A high availability cluster must maintain data integrity as one cluster node takes over control of a service from another cluster node. 
  • Node failures in a high availability cluster are not visible from clients outside the cluster. 
  • High availability clusters are sometimes referred to as failover clusters.




What is Load Balancing Cluster?
  • Load-balancing clusters dispatch network service requests to multiple cluster nodes to balance the request load among the cluster nodes. 
  • Load balancing provides cost-effective scalability because you can match the number of nodes according to load requirements. If a node in a load-balancing cluster becomes inoperative, the load-balancing software detects the failure and redirects requests to other cluster nodes. 
  • Node failures in a load-balancing cluster are not visible from clients outside the cluster. 
  • Load balancing is available with the Load Balancer Add-On.
What is a High Performance Cluster?
  • High-performance clusters use cluster nodes to perform concurrent calculations. 
  • A high-performance cluster allows applications to work in parallel, therefore enhancing the performance of the applications. 
  • High performance clusters are also referred to as computational clusters or grid computing.
How many nodes are supported in Red Hat 6 Cluster?
A cluster configured with qdiskd supports a maximum of 16 nodes. The reason for the limit is because of scalability; increasing the node count increases the amount of synchronous I/O contention on the shared quorum disk device.