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BR Design Principles

This document describes the design principles of Backup & Restore (BR), including its architecture and backup files.

BR architecture

BR sends a backup or restoration command to each TiKV node. After receiving the command, TiKV performs the corresponding backup or restoration operation.

Each TiKV node has a path in which the backup files generated in the backup operation are stored and from which the stored backup files are read during the restoration.

br-arch

Backup files

This section describes the design of backup files generated by BR.

Types of backup files

BR can generate the following types of backup files:

  • SST file: stores the data that the TiKV node backs up.
  • backupmeta file: stores the metadata of a backup operation, including the number, the key range, the size, and the Hash (sha256) value of the backup files.
  • backup.lock file: prevents multiple backup operations from storing data to the same directory.

Naming format of SST files

SST files are named in the format of storeID_regionID_regionEpoch_keyHash_cf. The fields in the format are explained as follows:

  • storeID is the TiKV node ID.
  • regionID is the Region ID.
  • regionEpoch is the version number of a Region.
  • keyHash is the Hash (sha256) value of the startKey of a range, which ensures the uniqueness of a key.
  • cf indicates the Column Family of RocksDB (default or write by default).

Storage format of SST files

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