What is Cluster? And Types of Clusters and how to setup
Cluster -- A cluster is a group of independent computers (nodes) that are presented to the network as a single system. There are different types of high availability solutions
NLB - Network Load Balancing Cluster, it works on network level but not at resource level. A server in the network load balancing cluster is known each other, when one server fails the other server automatically redistributes the connections among themselves. This offers horizontal scaling and you can simply add new server when network load increases. There will be no data sharing between the servers which are configured in NLB, it is widely used in few areas such as web servers, file servers, printer servers, terminal servers etc., This is primarily to distribute load (requests) to different nodes which are part of cluster.
NLB doesn’t require any special hardware, an NLB farm can include 32 nodes, but you can start with high availability with 2 nodes and nodes can increased when traffic increases. For setting up network load balancing all you need is 2 or more nodes connected to a common network and additional IP (Virtual IP) where the clients will connect to that IP. The virtual IP is used load balancing nodes in the NLB cluster.
Failover Cluster - A failover cluster is a group of independent computers or nodes which are physically connected by LAN and that are programmatically by cluster software. The group of nodes is worked together to increase the availability of applications and services that run on the cluster. In other words if NodeA fails then automatically the application will be served from NodeB that means the responsibilities of NodeA will takeover by NodeB.
The primary difference between NLB and failover cluster is NLB offers scalability and failover cluster cannot improve the scalability, it can only support high availability.
Setting up failover cluster is little complex, we need two networks public and private (heartbeat) and a shared drive (called Quorum) and an additional public IP in addition to 2 public ips and 2 private ips for two systems that we will have. We will see detailed terminology and setting up cluster in further posts.