Application-Consistent Backups

Application-consistent backups are used to back up entities with high or extremely high transaction loads. Good examples of such entities can be Microsoft SharePoint, Active Directory, MS SQL Server, or Oracle database solutions.

When such high-transactional solutions become subject to back up, the key point is the memory state and current transactions are stopped, flushed to disk, and only then are backed up.

If memory cannot be flushed to disk for some reason, backup may not be valid for restore or some important data may be missing.

Thus, an application-consistent backup is a backup that is equipped with tools to notify applications about coming backup operation and allow applications to achieve a quiescent and consistent state by flushing all operations to disk.

This chapter covers the following topics:

Frameworks for Application-Consistent Backups

Volume Shadow Copy Service (VSS) is a framework designed primarily to solve the application-consistent problems for Windows operating systems. VSS is an infrastructure that provides backup applications with the feature of creating application-consistent backups.

When backup job is initiated, VSS works as follows:

Every running application that needs to flush its data kept in RAM to disk is notified by VSS.
Then a Copy-On-Write operation is performed on volume.
A volume snapshot is done and can be processed by a backup application.

In case an application runs on a virtual machine on Hyper-V Server, a VSS-aware backup of the Hyper-V host, leveraging Hyper-V Integration Services, communicates with the VSS writers in the guest virtual machine to perform an application-consistent backup of the virtual machine and the applications on it

Application-Consistent Hyper-V Backups

You can configure the application-consistent options on the Application Processing Options step of the VMware backup wizard. These options can be configured separately for each virtual machine.

Click the application processing value to change it, if necessary.

By default, the Try application processing setting is set. You can change these options separately for each virtual machine, if necessary.

The following options are available:

Try application processing. Back up virtual machines 'as is' if failed. Once this option is selected, virtual machines are backed up one by one. The state of applications running on virtual machines is checked, then a recovery consistent checkpoint is made and an application-consistent backup is performed. In case an recovery consistent checkpoint cannot be not made for some reason, this virtual machine will be backed up 'as is'.
Require successful application processing. Skip virtual machines if failed. Once this option is selected, virtual machines with applications that did not flush pending I/O operations from memory to disks, are skipped and an appropriate warning is displayed for a user.
Disable application processing. Back up virtual machines 'as is'. Once this option is selected, regular VM snapshots are done without quiescing.