Failover
Switching operation to a standby system when the primary one fails.
Automatic failover happens without intervention and suits systems where any interruption is unacceptable. Manual failover requires a decision, which is slower but avoids flapping between sites over a transient fault.
The part that gets missed is failback: returning to the primary once it is healthy, without losing the data written while running on the standby.
Where this comes up
Failover sits inside our backup and disaster recovery work. If you are trying to work out what this means for your own environment rather than in the abstract, that is the page worth reading next, and a short call will get you a straight answer faster than either.
Related terms
Failback Returning operations to the primary system after running on a standby. Replication Continuously copying data or entire systems to a second location so a current copy is always available. Recovery time objective The maximum time a system can be unavailable before the impact becomes unacceptable. Uptime The proportion of time a system is available, usually expressed as a percentage over a period.