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Ryan Leung edited this page Jul 13, 2020
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The Placement Driver (PD) server is the managing component of the entire cluster and is in charge of the following three operations:
- Storing the metadata of the cluster such as the Region location of a specific key.
- Scheduling and load balancing Regions in the TiKV cluster, including but not limited to data migration and Raft group leader transfer.
- Allocating the transaction ID that is globally unique and monotonically increasing.
The PD server ensures redundancy by using the Raft consensus algorithm provided by etcd. The Raft leader is responsible for handling all operations, with remaining PD servers available for high availability only. It is recommended to deploy PD as an odd number of nodes.