Application-Consistent Backup

Description

There are three backup types in terms of backup consistency:

• Inconsistent backup: An inconsistent backup contains data taken from different points in time. This typically occurs if changes are made to your files or disks during the backup. CBR cloud server backup uses the consistency snapshot technology for disks to protect data of ECSs and BMSs. If you back up multiple cloud disks separately, the backup time points of the disks are different. As a result, the backup data of the disks is inconsistent.
• Crash-consistent backup: A crash-consistent backup captures all data on disks at the time of the backup and does not capture data in memory or any pending I/O operations. Although it cannot ensure application consistency, disks are checked by chkdsk upon OS restart to restore damaged data and undo logs are used by databases to keep data consistent.
• Application-consistent backup: An application-consistent backup captures data in memory or any pending I/O operations and allows applications to achieve a quiescent and consistent state.

Figure 1 compares these backup types in detail.

CBR supports both crash-consistent backup (also called cloud server backup) and application-consistent backup (also called database server backup).

Crash-consistent backup does not back up data in memory or pending I/O operations and cannot be used to restore applications. If your server is running a MySQL or SAP HANA database, you can use application-consistent backup. An application-consistent backup captures application information both in memory and in pending I/O operations and can be used to quickly restore applications.

Figure 1 Backup consistency

FAQ