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Redundancy and Replication

  • Redundancy is the duplication of critical components or functions of a system
    • with the intention of increasing the reliability of the system
      • usually in the form of a backup or fail-safe, or to improve actual system performance
    • e.g. if there is only one copy of a file stored on a single server, then losing that server means losing the file
      • Since losing data is seldom a good thing
        • we can create duplicate or redundant copies of the file to solve this problem
  • Redundancy plays a key role in removing the single points of failure in the system
    • provides backups if needed in a crisis
    • e.g. if we have two instances of a service running in production and one fails * the system can failover to the other one alt text
  • Replication means sharing information to ensure consistency between redundant resources
    • such as software or hardware components, to improve reliability, fault-tolerance, or accessibility
  • Replication is widely used in many database management systems (DBMS)
    • usually with a master-slave relationship between the original and the copies
    • The master gets all the updates
      • which then ripple through to the slaves
        • Each slave outputs a message stating that it has received the update successfully
          • thus allowing the sending of subsequent updates