# High Availability Features Of Tidb Database Cluster

+ TiDB database provides strong consistency.
+ Denial of service if strong consistency is not guaranteed.
+ If at least half of the replica of PD and TiKV are alive, node downtime or isolation is tolerated within a certain limit.
+ PD and TiKV can automatically fail over to most surviving replica.
+ TiDB Server does not guarantee that all nodes can provide services at the same time.
+ Troubleshooting is accompanied by a downgrade of service.

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1. The TiDB database provides strong consistency, and once new data is written, the new value can be read at any time from any replica.
2. Denial of service if strong consistency is not guaranteed.
3. If at least half of the replica of PD and TiKV are alive, tolerate node downtime or isolation within a certain limit.
4. PD and TiKV can automatically fail over to most surviving replica.
5. TiDB Server does not guarantee that all nodes can provide services at the same time, and requires the cooperation of the consumer for failover (relying on load balancers such as F5, HAProxy, etc.).
6. Failover can be accompanied by service degradation, such as reduced computing resources, delays due to failover, brief unavailability, or scheduling overhead.