VMware Consolidated Backup Workflow | Types of Backups | Performing Image-Level Virtual Machine Backups

VMware Consolidated Backup Workflow

Before using Consolidated Backup, you need to configure and schedule a backup job for each virtual machine or a group of virtual machines.

At the scheduled time, the backup software starts the backup job on the VCB proxy. When the backup job is launched, the following steps take place:

1	The backup software calls the pre-backup script, which performs these tasks:

a	(Optional) Runs your custom pre-freeze script in the virtual machine.

The pre-freeze script prepares the critical software components in the virtual machine for a backup. See below Running Custom Quiescing Scripts.

b	Quiesces the virtual machine.

c	Puts the virtual machine into snapshot mode.

Changes to virtual disks are stored for later writing. The virtual machine can continue to operate during this process.

d	Unquiesces the virtual machine that was quiesced in Step b.

e	(Optional) Runs your custom post-thaw script in the virtual machine.

The post-thaw script reverses any changes made by the pre-freeze script in Step a.

f	Makes the virtual machine snapshot available to the third-party software:

•	For image-level virtual machine backups, see below Performing Image-Level Virtual Machine Backups.

•	For file-level backups of Microsoft Windows virtual machines, see below Performing File-Level Virtual Machine Backups.

2	The backup software performs an ordinary backup of the virtual machine snapshot moving the data to a backup medium. The virtual machine can continue to operate during this process.

3	The backup software calls the post-backup script, which performs the following tasks:

a	Unmounts the virtual machine snapshot from the backup proxy.

b	Takes the virtual machine out of snapshot mode, committing to disk any changes made while the machine was in snapshot mode.

Types of Backups

Consolidated Backup supports image-level backups for virtual machines running any guest operating system and file-level backups for virtual machines running Microsoft Windows operating systems.

•

Image-level backup allows backup clients to make a copy of all virtual disks and configuration files associated with a particular virtual machine. This type of backup is suitable for restoring an entire virtual machine in the event of a hardware failure or a system administrator error, such as the accidental deletion of the virtual machine.

•	File-level backup allows backup clients to make copies of individual files contained within the virtual disks. File-level backups can be of the following types:

•	Full file backup — Backs up all files.

•	Differential backup — Backs up only files that have changed since the last full file backup.

•	Incremental backup — Backs up only files that have changed since the last backup, whether the last backup was full or incremental.

File-level backups allow files or directories to be restored individually. Use the file-level backups to prevent data loss due to user errors, such as accidental file deletion.

Performing Image-Level Virtual Machine Backups

An image-level virtual machine backup is operating-system neutral and can be performed regardless of the guest operating system.

When you run the image-level virtual machine backup, Consolidated Backup first creates a snapshot of your virtual machine. Then the following steps take place:

1	Consolidated Backup exports the virtual machine snapshot to a local directory on the VCB proxy. For example:

C:\mnt\mytestvm.foo.com-fullVM

2	The third-party backup software picks up the virtual machine disk images and configuration files and moves them to the backup medium.

Performing File-Level Virtual Machine Backups

For virtual machines running Windows, Consolidated Backup supports file-level backups.

When you run file-level backups, you first create a snapshot of your virtual machine. Then the following steps take place:

1	Consolidated Backup discovers volumes within virtual machine snapshots and mounts discovered volumes on the VCB proxy at predefined junction points.

Each junction point corresponds to a drive letter assigned to each volume in the virtual machine. For example:

C:\mnt\mytestvm.foo.com\letters\D

 

Caution Because the VCB proxy can recognize only volumes that have drive letters assigned to them, make sure that each volume on a virtual disk has a drive letter.

2	The third-party backup software makes file-level backups from these volumes.

Running Custom Quiescing Scripts

You can also run custom pre-freeze and post-thaw quiescing scripts to create a quiescent snapshot of your virtual machine. For example, use the scripts to achieve application-consistent backups in Windows virtual machines that do not support the VSS components. Deploy and run the custom quiescing scripts inside the protected virtual machine. Table 2-3 shows the directories, in which the pre-freeze and post-thaw scripts should be placed.

When running the scripts, you can also use the SYNC driver or VSS components on those virtual machines that support them.

 

Table 2-3. Locations of Custom Quiescing Scripts 

Guest Operating System	Script	Location on Virtual Machines Hosted by ESX Server 3.5 U1 and Earlier	Location on Virtual Machines Hosted by ESX Server 3.5 U2 and Later
Windows	Pre-freeze	C:\Windows\pre-freeze-script.bat	C:\Program Files\VMware\VMware Tools\backupScripts.d All scripts are invoked in ascending alphabetical order with freeze as the first argument.
	Post-thaw	C:\Windows\post-thaw-script.bat	C:\Program Files\VMware\VMware Tools\backupScripts.d All scripts are invoked in descending alphabetical order with thaw or freezeFail as the first argument.
Other	Pre-freeze	/usr/sbin/pre-freeze-script	/usr/sbin/pre-freeze-script
	Post-thaw	/usr/sbin/post-thaw-script	/usr/sbin/post-thaw-script

When running the scripts, Consolidated Backup performs the following steps:

1	Runs the pre-freeze script inside the virtual machine being backed up.

For the script’s location, see Table 2-3.

If the pre-freeze script returns a nonzero exit code, the snapshot create operation fails.

2	(Optional) Engages either the SYNC driver or VSS components.

For information on the virtual machines that support the SYNC driver and VSS components, see Table 2-2.

If this step fails, Consolidated Backup proceeds to Step 5.

3	Creates a snapshot.

4	Disengages the SYNC driver or the VSS components.

This step can fail if the snapshot creation in Step 3 took too long and timed out.

5	Runs the post-thaw script inside the virtual machine.

If successful, the exit status of this script is 0.

Share this

ChinniLax