Back up Data to PV

This document describes how to back up the data of a TiDB cluster on Kubernetes to Persistent Volumes (PVs). PVs in this documentation can be any Kubernetes supported PV types. This document uses NFS as an example PV type.

The backup method described in this document is implemented based on CustomResourceDefinition (CRD) in TiDB Operator. For the underlying implementation, BR is used to get the backup data of the TiDB cluster, and then send the data to PVs. BR stands for Backup & Restore, which is a command-line tool for distributed backup and recovery of the TiDB cluster data.

Usage scenarios

If you have the following backup needs, you can use BR to make an ad-hoc backup or scheduled snapshot backup of the TiDB cluster data to PVs:

To back up a large volume of data at a fast speed
To get a direct backup of data as SST files (key-value pairs)

For other backup needs, refer to Backup and Restore Overview to choose an appropriate backup method.

Note

BR is only applicable to TiDB v3.1 or later releases.
Data that is backed up using BR can only be restored to TiDB instead of other databases.

Ad-hoc backup

Ad-hoc backup supports both snapshot backup and incremental backup.

To get an Ad-hoc backup, you need to create a Backup Custom Resource (CR) object to describe the backup details. Then, TiDB Operator performs the specific backup operation based on this Backup object. If an error occurs during the backup process, TiDB Operator does not retry, and you need to handle this error manually.

This document provides an example about how to back up the data of the demo1 TiDB cluster in the test1 Kubernetes namespace to NFS. The following are the detailed steps.

Step 1: Prepare for an ad-hoc backup

Download backup-rbac.yaml to the server that runs the backup task.
Execute the following command to create the role-based access control (RBAC) resources in the test1 namespace:
```
kubectl apply -f backup-rbac.yaml -n test1
```

Make sure that the NFS server is accessible from your Kubernetes cluster, and you have configured TiKV to mount the same NFS server directory to the same local path as in backup jobs. To mount NFS for TiKV, refer to the configuration below:

spec:
  tikv:
    additionalVolumes:
    # Specify volume types that are supported by Kubernetes, Ref: https://kubernetes.io/docs/concepts/storage/persistent-volumes/#types-of-persistent-volumes
    - name: nfs
      nfs:
        server: 192.168.0.2
        path: /nfs
    additionalVolumeMounts:
    # This must match `name` in `additionalVolumes`
    - name: nfs
      mountPath: /nfs

For a TiDB version earlier than v4.0.8, you also need to complete the following preparation steps. For TiDB v4.0.8 or a later version, skip these preparation steps.
1. Make sure that you have the SELECT and UPDATE privileges on the mysql.tidb table of the backup database so that the Backup CR can adjust the GC time before and after the backup.
2. Create the backup-demo1-tidb-secret secret to store the account and password to access the TiDB cluster:
```
kubectl create secret generic backup-demo1-tidb-secret --from-literal=password=${password} --namespace=test1
```

Step 2: Perform an ad-hoc backup

Create the Backup CR, and back up cluster data to NFS as described below:
```
kubectl apply -f backup-nfs.yaml
```
The content of backup-nfs.yaml is as follows:
```
---
apiVersion: pingcap.com/v1alpha1
kind: Backup
metadata:
  name: demo1-backup-nfs
  namespace: test1
spec:
  # backupType: full
  br:
    cluster: demo1
    clusterNamespace: test1
    # logLevel: info
    # statusAddr: ${status-addr}
    # concurrency: 4
    # rateLimit: 0
    # checksum: true
    # options:
    # - --lastbackupts=420134118382108673
  local:
    prefix: backup-nfs
    volume:
      name: nfs
      nfs:
        server: ${nfs_server_ip}
        path: /nfs
    volumeMount:
      name: nfs
      mountPath: /nfs
```
When configuring backup-nfs.yaml, note the following:
- If you want to back up data incrementally, you only need to specify the last backup timestamp --lastbackupts in spec.br.options. For the limitations of incremental backup, refer to Use BR to Back up and Restore Data.
- spec.local refers to the configuration related to PVs. For more information about PV configuration, refer to Local storage fields.
- Some parameters in spec.br are optional, such as logLevel, statusAddr, concurrency, rateLimit, checksum, and timeAgo. For more information about spec.br fields, refer to BR fields.
- For v4.0.8 or a later version, BR can automatically adjust tikv_gc_life_time. You do not need to configure spec.tikvGCLifeTime and spec.from fields in the Backup CR.
- For more information about the Backup CR fields, refer to Backup CR fields.
After creating the Backup CR, TiDB Operator automatically starts the backup task. You can use the following command to check the backup status:
```
kubectl get bk -n test1 -owide
```

Backup CR examples

Back up data of all clusters

---
apiVersion: pingcap.com/v1alpha1
kind: Backup
metadata:
  name: demo1-backup-nfs
  namespace: test1
spec:
  # backupType: full
  br:
    cluster: demo1
    clusterNamespace: test1
  local:
    prefix: backup-nfs
    volume:
      name: nfs
      nfs:
        server: ${nfs_server_ip}
        path: /nfs
    volumeMount:
      name: nfs
      mountPath: /nfs

Back up data of a single database

The following example backs up data of the db1 database.

---
apiVersion: pingcap.com/v1alpha1
kind: Backup
metadata:
  name: demo1-backup-nfs
  namespace: test1
spec:
  # backupType: full
  tableFilter:
  - "db1.*"
  br:
    cluster: demo1
    clusterNamespace: test1
  local:
    prefix: backup-nfs
    volume:
      name: nfs
      nfs:
        server: ${nfs_server_ip}
        path: /nfs
    volumeMount:
      name: nfs
      mountPath: /nfs

Back up data of a single table

The following example backs up data of the db1.table1 table.

---
apiVersion: pingcap.com/v1alpha1
kind: Backup
metadata:
  name: demo1-backup-nfs
  namespace: test1
spec:
  # backupType: full
  tableFilter:
  - "db1.table1"
  br:
    cluster: demo1
    clusterNamespace: test1
  local:
    prefix: backup-nfs
    volume:
      name: nfs
      nfs:
        server: ${nfs_server_ip}
        path: /nfs
    volumeMount:
      name: nfs
      mountPath: /nfs

Back up data of multiple tables using the table filter

The following example backs up data of the db1.table1 table and db1.table2 table.

---
apiVersion: pingcap.com/v1alpha1
kind: Backup
metadata:
  name: demo1-backup-nfs
  namespace: test1
spec:
  # backupType: full
  tableFilter:
  - "db1.table1"
  - "db1.table2"
  br:
    cluster: demo1
    clusterNamespace: test1
  local:
    prefix: backup-nfs
    volume:
      name: nfs
      nfs:
        server: ${nfs_server_ip}
        path: /nfs
    volumeMount:
      name: nfs
      mountPath: /nfs

Scheduled snapshot backup

You can set a backup policy to perform scheduled backups of the TiDB cluster, and set a backup retention policy to avoid excessive backup items. A scheduled snapshot backup is described by a custom BackupSchedule CR object. A snapshot backup is triggered at each backup time point. Its underlying implementation is the ad-hoc snapshot backup.

Step 1: Prepare for a scheduled snapshot backup

The steps to prepare for a scheduled snapshot backup are the same as that of Prepare for an ad-hoc backup.

Step 2: Perform a scheduled snapshot backup

Create the BackupSchedule CR, and back up cluster data as described below:

kubectl apply -f backup-schedule-nfs.yaml

The content of backup-schedule-nfs.yaml is as follows:

 ---
 apiVersion: pingcap.com/v1alpha1
 kind: BackupSchedule
 metadata:
   name: demo1-backup-schedule-nfs
   namespace: test1
 spec:
   #maxBackups: 5
   #pause: true
   maxReservedTime: "3h"
   schedule: "*/2 * * * *"
   backupTemplate:
     br:
       cluster: demo1
       clusterNamespace: test1
       # logLevel: info
       # statusAddr: ${status-addr}
       # concurrency: 4
       # rateLimit: 0
       # checksum: true
     local:
       prefix: backup-nfs
       volume:
         name: nfs
         nfs:
           server: ${nfs_server_ip}
           path: /nfs
       volumeMount:
         name: nfs
         mountPath: /nfs

From the backup-schedule-nfs.yaml example above, you can see that the backupSchedule configuration consists of two parts. One is the unique configuration of backupSchedule, and the other is backupTemplate.

For the unique configuration of backupSchedule, refer to BackupSchedule CR fields.
backupTemplate specifies the configuration related to the cluster and remote storage, which is the same as the spec configuration of the Backup CR.

After creating the scheduled snapshot backup, use the following command to check the backup status:
```
kubectl get bks -n test1 -owide
```
Use the following command to check all the backup items:
```
kubectl get bk -l tidb.pingcap.com/backup-schedule=demo1-backup-schedule-nfs -n test1
```

Delete the backup CR

If you no longer need the backup CR, refer to Delete the Backup CR.

Troubleshooting

If you encounter any problem during the backup process, refer to Common Deployment Failures.