Kristof Kovacs

Software architect, consultant

High-availability clusters

High-availability, load-balanced Linux and FreeBSD cloud solutions can be the key to business continuity for modern, Internet-reliant firms.

high availability cluster

Usually, such clusters include:

  • No single point of failure
  • HTTP acceleration and load balancing using HAProxy, Varnish or Nginx
  • MySQL or PostgreSQL replication
  • Separation of DB read and write operations (reads go to slaves for better performance)
  • Failover with keepalived or Cloud-specific solutions like AWS's ELB
  • Sessions in memory-mapped disk or in Redis, or sessionless operation
  • Shared disks via NFS and/or DRBD/GFS
  • SQL tuning
  • Web server (Apache, Nginx) tuning
  • Operating system tuning (Linux, FreeBSD)
  • A monitoring system
  • Hardware can be physical (for high-availibility) or virtualized (for load-balancing)
  • Infrastructure-as-code for fast provisioning with Ansible or SaltStack

When the cluster is for a specific application (not just general web hosting), then we can also achieve big gains by application specific tuning.

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