Physically, data is stored in RocksDB ● We build a Raft layer on top of RocksDB ○ What is Raft? ● Written in Rust! TiKV API (gRPC) Transaction MVCC Raft (gRPC) RocksDB Raw KV API (https://github chkv/main.go) RocksDB Instance Region 1:[a-e] Region 3:[k-o] Region 5:[u-z] ... Region 4:[p-t] RocksDB Instance Region 1:[a-e] Region 2:[f-j] Region 4:[p-t] ... Region 3:[k-o] RocksDB Instance Instance Region 2:[f-j] Region 5:[u-z] Region 3:[k-o] ... RocksDB Instance Region 1:[a-e] Region 2:[f-j] Region 5:[u-z] ... Region 4:[p-t] Raft group Storage stack 2/2 ● Data is organized by Regions

TiKV Key Space [ start_key, end_key) (-∞, +∞) Sorted Map RPC (gRPC) Transaction MVCC Raft RocksDB Node B Node C Node A Raft Raft Raft 256MB PD - Overview TiKV TiKV TiKV TiKV … ... TiKV Cluster

=> [1,dongxu,huang@pingcap.com] t101_r2 => [2, foo, bar@pingcap.com] t101_r… => ... 存储层 Local RocksDB instance t101_r1 ... t102_r2 ... ... ... t105_i1_1 ... t105_i1_2 ... ● For a row in a Table