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Hot spare

(also warm spare, hot standby)

Hot spare definition

A hot spare is a backup component or device that is kept ready and available to replace a failed or faulty component in a system. It is “hot“ because it is powered on and prepared to take over immediately. The hot spare is a reliable replacement, providing continuity and keeping the system functioning when a failure occurs.

Hot spare examples

  • RAID arrays. In a redundant array of independent disks (RAID), hot spare drives are maintained in the system. If one of the active drives fails, the hot spare is automatically activated to replace it, ensuring uninterrupted data storage and system availability.
  • Power supply units (PSUs). Some computer systems, especially servers, may have redundant power supply units. If one PSU fails, the hot spare PSU takes over immediately, ensuring a continuous power supply and preventing system downtime.
  • Network devices. In enterprise networking environments, hot spare switches or routers can be configured to automatically take over if the primary device fails.
  • Uninterruptible power supplies (UPS). UPS systems often have hot spare batteries. If the primary battery fails or loses power, the hot spare battery provides continuous power backup, protecting connected devices from power outages.
  • HVAC systems. Large-scale heating, ventilation, and air conditioning (HVAC) systems may have hot spare components like pumps or chillers. If a primary component fails, the hot spare maintains the desired temperature and environmental conditions.
  • Data centers. Critical infrastructure in data centers, such as servers, switches, and storage devices, often have hot spare components configured to provide immediate failover in case of hardware failures, minimizing service disruptions and downtime.

Hot spare advantages

  • Minimized downtime. Hot spares reduce downtime by automatically taking over for failed components.
  • Data protection. Hot spares help protect valuable data by swiftly replacing failed drives or components.
  • Business continuity. Hot spares allow businesses to continue operating without interruptions.
  • Simplified maintenance. Hot spares simplify maintenance procedures and make replacing faulty components easier.
  • Improved reliability. By having hot spares readily available, systems become more reliable.
  • Cost-effective. Hot spares make systems resilient and offer backup solutions without additional dedicated equipment.