# `HA` of `TiDB/TiKV`
+ Tolerate node downtime or isolation within a certain limit
  + More than half replicas survive
+ Does NOT guarantee that all nodes provide services at the same time
  + Need applications to do failover (load balancer, `HAProxy`, etc)
+ Performance degradation during failover
  + Reduction of computing resources
  + Latency caused by failover
  + Scheduling overhead
+ Consistency over availability
  + Denial of service if cannot guarantee consistency
  + Provide tools to recover from disaster (give up consistency)
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