Important

You are viewing the documentation of TiDB v6.0 (DMR). PingCAP does not provide bug fixes for v6.0. Any bugs will be fixed in future releases.

For general purposes, please use the latest LTS version of the TiDB database.

Use BR to Restore Cluster Data

This document describes how to restore cluster data using BR in the following scenarios:

If you are not familiar with Backup & Restore (BR), it is recommended that you read the following documents to fully understand BR usage principles and methods:

Restore TiDB cluster snapshots

BR supports restoring snapshot backup on an empty cluster to restore the target cluster to the latest state when the snapshot is backed up.

Example: Restore the snapshot generated at 2022-01-30 07:42:23 from the 2022-01-30/ directory in the backup-data bucket of Amazon S3 to the target cluster.

br restore full \
    --pd "${PDIP}:2379" \
    --storage "s3://backup-data/2022-01-30/" \
    --ratelimit 128 \
    --log-file restorefull.log

In the preceding command,

  • --ratelimit: The maximum speed for each TiKV to perform a restoration task (unit: MiB/s)
  • --log-file The target file for BR logging

During restoration, a progress bar is displayed in the terminal, as shown below. When the progress bar advances to 100%, the restoration is complete. To ensure data security, BR performs a check on the restored data.

br restore full \
    --pd "${PDIP}:2379" \
    --storage "s3://backup-data/2022-01-30/" \
    --ratelimit 128 \
    --log-file restorefull.log
Full Restore <---------/...............................................> 17.12%.

Restore a database or a table

BR supports restoring partial data of a specified database or table from backup data. This feature allows you to filter out unwanted data and back up only a specific database or table.

Restore a database

To restore a database to the cluster, run the br restore db command. To get help on this command, run the br restore db --help command.

Example: Restore the test database from the db-test/2022-01-30/ directory in the backup-data bucket of Amazon S3 to the target cluster.

br restore db \
    --pd "${PDIP}:2379" \
    --db "test" \
    --ratelimit 128 \
    --storage "s3://backup-data/db-test/2022-01-30/" \
    --log-file restore_db.log

In the preceding command, --db specifies the name of the database to be restored, and other parameters are the same as those in Restore TiDB cluster snapshots.

Note

When you restore the backup data, the database name specified by --db must be the same as the one specified by -- db in the backup command. Otherwise, the restoration fails. This is because the metafile of the backup data ( backupmeta file) records the database name, and you can only restore data to the database with the same name. The recommended method is to restore the backup data to the database with the same name in another cluster.

Restore a table

To restore a single table to the cluster, run the br restore table command. To get help on this command, run the br restore table --help command.

Example: Restore test.usertable from the table-db-usertable/2022-01-30/directory in the backup-data bucket of Amazon S3 to the target cluster.

br restore table \
    --pd "${PDIP}:2379" \
    --db "test" \
    --table "usertable" \
    --ratelimit 128 \
    --storage "s3://backup-data/table-db-usertable/2022-01-30/" \
    --log-file restore_table.log

In the preceding command, --table specifies the name of the table to be restored, and other parameters are the same as those in Restore TiDB cluster snapshots.

Restore multiple tables with table filter

To restore multiple tables with more criteria, run the br restore full command and specify the table filters with --filter or -f.

Example: Restore data matching the db*.tbl* table from the table-filter/2022-01-30/ directory in the backup-data bucket of Amazon S3 to the target cluster.

br restore full \
    --pd "${PDIP}:2379" \
    --filter 'db*.tbl*' \
    --storage "s3://backup-data/table-filter/2022-01-30/"  \
    --log-file restorefull.log

Restore backup data from external storage

BR supports restoring data to Amazon S3, Google Cloud Storage (GCS), Azure Blob Storage, NFS, or other S3-compatible file storage services. For details, see the following documents:

Restore incremental data

Warning

This is still an experimental feature. It is NOT recommended that you use it in the production environment.

Restoring incremental data is similar to restoring full data using BR. When restoring incremental data, make sure that all the data backed up before last backup ts has been restored to the target cluster. Also, because incremental restoration updates ts data, you need to ensure that there are no other writes during the restoration. Otherwise, conflicts might occur.

br restore full \
    --pd "${PDIP}:2379" \
    --storage "s3://backup-data/2022-01-30/incr"  \
    --ratelimit 128 \
    --log-file restorefull.log

Restore encrypted backup data

Warning

This is still an experimental feature. It is NOT recommended that you use it in the production environment.

After encrypting the backup data, you need to pass in the corresponding decryption parameters to restore the data. Ensure that the decryption algorithm and key are correct. If the decryption algorithm or key is incorrect, the data cannot be restored.

br restore full\
    --pd ${PDIP}:2379 \
    --storage "s3://backup-data/2022-01-30/" \
    --crypter.method aes128-ctr \
    --crypter.key 0123456789abcdef0123456789abcdef

Restore tables created in the mysql schema

Warning

This is still an experimental feature. It is NOT recommended that you use it in the production environment.

BR backs up tables created in the mysql schema by default. When you restore data using BR, the tables created in the mysql schema are not restored by default. To restore these tables, you can explicitly include them using the table filter. The following example restores mysql.usertable created in the mysql schema. The command restores mysql.usertable along with other data.

br restore full -f '*.*' -f '!mysql.*' -f 'mysql.usertable' -s $external_storage_url --ratelimit 128

In the preceding command,

  • -f '*.*' is used to override the default rules
  • -f '!mysql.*' instructs BR not to restore tables in mysql unless otherwise stated.
  • -f 'mysql.usertable' indicates that mysql.usertable should be restored.

If you only need to restore mysql.usertable, run the following command:

br restore full -f 'mysql.usertable' -s $external_storage_url --ratelimit 128
Warning

Although you can back up system tables (such as mysql.tidb) using BR, BR ignores the following system tables even if you use the --filter setting to perform the restoration:

  • Statistical information tables (mysql.stat_*)
  • System variable tables (mysql.tidb, mysql.global_variables)
  • User information tables (such as mysql.user and mysql.columns_priv)
  • Other system tables

Compatibility issues might occur when restoring system tables. Therefore, avoid restoring system tables in production environments.

Restoration performance and impact

  • TiDB fully uses TiKV CPU, disk IO, network bandwidth, and other resources when restoring data. Therefore, it is recommended that you restore backup data on an empty cluster to avoid affecting running services.
  • The restoration speed depends much on cluser configuration, deployment, and running services. Generally, the restoration speed can reach 100 MB/s (per TiKV node).
Note

The preceding test conclusions, based on simulation tests in many scenarios and verified in some customer sites, are worthy of reference. However, the restoration speed may vary depending on the scenarios. Therefore, you should always run the test and verify the test results.

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