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Understanding Linux Cluster

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 Thanks for visiting RvKmR's blogs.

 So, What means of clusters and why we need them. Cluster is set of servers or say computers working together to achieve single goal or a task. Now you may have idea why we need cluster. 

Types of Cluster:
  • High Availability Cluster / HA Cluster
    •  HA Cluster again grouped in two types.
      1. Active-Active Cluster
      2. Active-Passive Cluster
In Active-Active Cluster Service is running on all nodes in cluster. That means all nodes serving independently.
In Active-Passive Cluster Service is running on one of node from cluster and other nodes in passive state. If primary node fails then only other node in cluster will start service.  
  • Storage Cluster
In this cluster type, all members provides a single cluster file system that can be accessed by different servers. These file system can be used to read-write data simultaneously. EX: GFS2 


OK, Then what is High Availability. This type of cluster provides high availability of service which is hosted on cluster even one of server from cluster is down or not serving requests for hosted service. Not clear yet, OK, lets consider cluster of two nodes A and B. For now lets say Service is running on Node A, but suddenly node A stopped responding. In that case Node B will detect that Node A is not serving, and now its time to start service on Node B.  
High availability cluster known as Fail-over cluster. \

 Below are some of important points that we need to understand before starting configuring.

  • Resource and Resources Group
  • Fencing
  • Shared Storage
  • Quorum  


We will discuss those topics in next blogs.
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