The following figure shows the physical backup architecture of OceanBase Database.
After you log on to the standby cluster in a system tenant, you must first initiate log archiving by using SQL statements. You can perform the baseline backup operation only after log archiving is initiated.
Log archiving will regularly back up logs to the backup destination. You only need to run the "alter system archivelog" statement once, and log archiving backs up logs regularly in the background. During log archiving, the leader of each partition group (PG) is responsible for regularly archiving the logs of that PG to the specified path of the backup medium. The RootService (RS) is responsible for regularly counting the log archiving progress and updating it to the internal table.
Data backup needs to be triggered by users. Generally, the full backup is triggered on Saturday and the incremental backup is triggered on Tuesday and Thursday. When you initiate a data backup request, the request is first forwarded to the node where the RS is located. RS generates a data backup task based on the current tenant and the PG contained by the tenant. Then, RS distributes the backup task to the OBServer for execution in parallel. The OBServer is responsible for backing up the meta information and macroblocks of the PG to the specified backup directory. The macroblocks are managed in units of PG.
Currently, OceanBase supports both the Object Storage Service (OSS) and Network File System (NFS) as the backup destinations. The following diagram shows the directory structure created by the backup function at the backup destination and the file types saved at each directory level.
backup/ # The root directory of backups
└── ob1 # cluster_name
└── 1 # cluster_id
└── incarnation_1 # The incarnation ID.
├── 1001 # The tenant ID.
│ ├── clog # The root directory of CLOG files.
│ │ ├── 1 # The Round ID of the CLOG backups.
│ │ │ ├── data # The data directory of logs.
│ │ │ └── index # The index directory of logs.
│ │ └── tenant_clog_backup_info # The meta information of log backups that is recorded by round ID.
│ └── data # The root directory of the data.
│ ├── backup_set_1 # The full backup directory.
│ │ ├── backup_1 # The first differential backup directory. The meta information is fully backed up.
│ │ ├── backup_2 # The second differential backup directory. The meta information is also fully backed up.
│ │ ├── backup_set_info # The directory that records the information of multiple differential backups in the backup_set directory.
│ │ └── data # The directory of the macroblock data, which contains all full and differential macro-block backup data.
│ └── tenant_data_backup_info # The directory that records all data backup information of the tenant.
├── clog_info # The backup information of server startup logs.
│ └── 1_xx.xx.xx.xx_12533 # A piece of startup log backup information of a server.
├── cluster_clog_backup_info # The cluster-level log backup information.
├── cluster_data_backup_info # The cluster-level data backup information.
├── tenant_info # The tenant information.
└── tenant_name_info # The mapping relationship between the tenant name and tenant ID.