BR: refine BR docs

TOC.md

@@ -130,17 +130,9 @@
     - [Use TiUP (Recommended)](/scale-tidb-using-tiup.md)
     - [Use TiDB Operator](https://docs.pingcap.com/tidb-in-kubernetes/stable/scale-a-tidb-cluster)
   - Backup and Restore
-    - Use BR Tool (Recommended)
-      - [BR Tool Overview](/br/backup-and-restore-tool.md)
-      - [Use BR Command-line for Backup and Restoration](/br/use-br-command-line-tool.md)
-      - [BR Use Cases](/br/backup-and-restore-use-cases.md)
-      - External Storages
-        - [External Storages Overview](/br/backup-and-restore-storages.md)
-        - [Back up and Restore Data on Azure Blob Storage](/br/backup-and-restore-azblob.md)
-      - BR Features
-        - [Auto Tune](/br/br-auto-tune.md)
-        - [Batch Create Table](/br/br-batch-create-table.md)
-      - [BR FAQ](/br/backup-and-restore-faq.md)
+    - [Use BR to Back Up Cluster Data](/br/br-usage-backup.md)
+    - [Use BR to Restore Cluster Data](/br/br-usage-restore.md)
+    - [BR Use Cases](/br/backup-and-restore-use-cases.md)
   - [Configure Time Zone](/configure-time-zone.md)
   - [Daily Checklist](/daily-check.md)
   - [Maintain TiFlash](/tiflash/maintain-tiflash.md)
@@ -454,13 +446,23 @@
       - [Handle Errors](/dm/dm-error-handling.md)
     - [Release Notes](/dm/dm-release-notes.md)
   - Backup & Restore (BR)
-    - [BR Tool Overview](/br/backup-and-restore-tool.md)
-    - [Use BR Command-line for Backup and Restoration](/br/use-br-command-line-tool.md)
+    - [BR Overview](/br/backup-and-restore-overview.md)
+    - [Deploy and Use BR](/br/br-deployment.md)
+    - [Use BR to Back Up Cluster Data](/br/br-usage-backup.md)
+    - [Use BR to Restore Cluster Data](/br/br-usage-restore.md)
     - [BR Use Cases](/br/backup-and-restore-use-cases.md)
-    - [External Storages](/br/backup-and-restore-storages.md)
     - BR Features
       - [Auto Tune](/br/br-auto-tune.md)
-    - [BR FAQ](/br/backup-and-restore-faq.md)
+      - [Batch Create Table](/br/br-batch-create-table.md)
+    - References
+      - [BR Design Principles](/br/backup-and-restore-design.md)
+      - [BR Command-line](/br/use-br-command-line-tool.md)
+      - [External Storages](/br/backup-and-restore-storages.md)
+      - [Back Up and Restore Data on Amazon S3 Using BR](/br/backup-storage-S3.md)
+      - [Back Up and Restore Data on Azure Blob Storage Using BR](/br/backup-storage-azblob.md)
+      - [Back Up and Restore Data on Google Cloud Storage Using BR](/br/backup-storage-gcs.md)
+      - [Back Up and Restore RawKV](/br/rawkv-backup-and-restore.md)
+      - [BR FAQs](/br/backup-and-restore-faq.md)
   - TiDB Binlog
     - [Overview](/tidb-binlog/tidb-binlog-overview.md)
     - [Quick Start](/tidb-binlog/get-started-with-tidb-binlog.md)

_index.md

@@ -59,7 +59,7 @@ Designed for the cloud, TiDB provides flexible scalability, reliability and secu
 
 - [Upgrade TiDB Using TiUP](/upgrade-tidb-using-tiup.md)
 - [Scale TiDB Using TiUP](/scale-tidb-using-tiup.md)
-- [Back up and Restore Data](/br/backup-and-restore-tool.md)
+- [Back up and Restore Data](/br/backup-and-restore-overview.md)
 - [Deploy and Manage TiCDC](/ticdc/manage-ticdc.md)
 - [Maintain TiDB Using TiUP](/maintain-tidb-using-tiup.md)
 - [Maintain TiFlash](/tiflash/maintain-tiflash.md)

br/backup-and-restore-design.md

@@ -0,0 +1,43 @@
+---
+title: BR Design Principles
+summary: Learn about the design details of BR.
+---
+
+# 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](/media/br-arch.png)
+
+## 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
+
+- For details about the storage format of SST files, see [Rocksdb BlockBasedTable Format](https://github.com/facebook/rocksdb/wiki/Rocksdb-BlockBasedTable-Format).
+- For details about the encoding format of backup data in SST files, see [Mapping of table data to Key-Value](/tidb-computing.md#mapping-of-table-data-to-key-value).