serverclusters

Server clusters are groups of connected servers that work together to appear as a single system to clients. The cluster coordinates resources and services to provide high availability, scalability, and/or high performance. Nodes share a common management plane and may rely on shared storage or distributed data replication.

Key components include cluster nodes, a cluster manager, a communication fabric (heartbeat), a quorum mechanism, and fencing to isolate failing nodes. Shared storage or distributed storage systems enable data access across nodes.

Common cluster types include high-availability clusters that automatically fail over services; load-balancing clusters that distribute traffic across nodes; compute clusters for parallel processing; database clusters with replicated or sharded data; and storage clusters that aggregate capacity and resilience.

Deployment patterns include active-active where multiple nodes serve requests simultaneously; active-passive where a standby node takes over; shared storage versus shared-nothing architectures; and rolling upgrades to minimize downtime. Quorum ensures decisions are made only when a majority of nodes are visible, and fencing prevents split-brain.

Management involves monitoring, health checks, automated failover, resource scheduling, and upgrades. Tools include Pacemaker and Corosync for traditional clusters; Kubernetes for containerized workloads; and load balancers or reverse proxies for traffic distribution.

Benefits include reduced downtime, load distribution, maintenance without interruption, and scalability. Challenges include complexity, data consistency in distributed systems, network latency, potential split-brain, licensing and cost.

Common workloads include web services, databases (for example MySQL or PostgreSQL clustering), HPC workloads, and distributed storage systems like Ceph or GlusterFS, as well as virtualization platforms with HA features.

Server clusters remain foundational for enterprise reliability and performance.