TiKV config: add capacity (#7665) (#7830)

tikv-configuration-file.md

@@ -416,6 +416,11 @@ Configuration items related to Raftstore
 + Enables or disables `prevote`. Enabling this feature helps reduce jitter on the system after recovery from network partition.
 + Default value: `true`
 
+### `capacity`
+
++ The storage capacity, which is the maximum size allowed to store data. If `capacity` is left unspecified, the capacity of the current disk prevails. To deploy multiple TiKV instances on the same physical disk, add this parameter to the TiKV configuration. For details, see [Key parameters of the hybrid deployment](/hybrid-deployment-topology.md#key-parameters).
++ Default value: `0`
+
 ### `raftdb-path`
 
 + The path to the Raft library, which is `storage.data-dir/raft` by default