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Druva Documentation

VMware functionalities in Phoenix

Phoenix Editions: File:/tick.png Business File:/cross.png Enterprise File:/tick.png Elite

Changed Block Tracking

VMware provides the Changed Block Tracking (CBT) capability that Phoenix uses to analyze and backup virtual machines in an optimal way.

CBT is a VMware feature that helps perform incremental backups. CBT identifies and tracks block changes since the last backup, and stores these changes in log form. This translates to increased backup speeds, reduced backup window, and reduced size of data being transferred.

The Auto-enable CBT feature provides a way to automatically enable CBT for configured virtual machines through Phoenix instead of an administrator doing it manually. The CBT setting is part of backup policy. Phoenix will try to enable CBT before the backup schedule kicks in for virtual machine(s). There should be no user snapshots on the virtual machine for this feature to work. In case there are user snapshots present on the virtual machine, Phoenix will run a full scan to backup the changed blocks. To know more about CBT, see Changed Block Tracking in the VMware documentation library. 

Note:

  • By default, the CBT option is enabled in the Phoenix backup policy.
  • If CBT(Change Block Tracking) is enabled, Thin disk are restored as Thin disk.
  • If CBT is disabled Thin disk are restored as Thick Disk Eager Zeroed.
  • Thick Disk (Both Eager and Lazy Zeroed) are always restored as Thick Disk Eager Zeroed.
  • CBT is always disabled on a restored virtual machine, even if CBT was enabled on the original virtual machine.
  • You may see VMWARE_VMOMI13 error if the CBT of virtual machine is not set correctly and the backup proxy version is less than 4.4. For more information on the error, see VMware VMOMI errors.
  • The source data size or changed data size is determined based on the size reported by the CBT APIs of VMware.

The CBT status for each VMware is displayed under the configured virtual machine tab and  the status is refreshed every 24 hours.

Note: Clearing the "Auto-enable CBT" check box does not imply that CBT is disabled for virtual machine. The "Auto-enable CBT" option is only for auto enablement of CBT and not to disable CBT . For more information on CBT behavior, see the table below.

The following table illustrates the CBT state and the systems expected behavior: 

Situation Expected Result
If CBT is disabled and " Auto‐enable CBT" : Yes

Snapshots present

Run full scan of virtual machine(s).

Snapshots not present

Enable CBT and read changed blocks for incremental backup. If for some reason Phoenix is not able to enable CBT, backup will fail.

If CBT is disabled and " Auto‐enable CBT" : No

Snapshots present

Run full scan of virtual machine(s).

Snapshots not present

Run full scan of virtual machine(s).

If CBT is previously enabled correctly, Auto-enable CBT --> Yes OR No 

Snapshots  present

Read changed blocks for incremental backup.

Snapshots not present

Read changed blocks for incremental backup.

If CBT is enabled but in inconsistent state and  "Auto‐enable CBT": Yes

Snapshots  present

Run full scan of virtual machine(s).

Snapshots not present

CBT is reset  and read changed blocks for incremental backup.

If CBT is enabled but in inconsistent state, and "Auto‐enable CBT": No

Snapshots  present

Run full scan of virtual machine(s).

Snapshots not present

Run full scan of virtual machine(s).

Note:  Do not run the vmcontrol command and auto enable CBT run simultaneously.

To know if Phoenix is running a full scan, view the progress log for the job. The following is an example of the progress log for a full scan:

Edit CBT options

You can edit the CBT options when you:

  1. Configure virtual machines
  2. Reconfigure virtual machine
  3. Add a VMware backup policy

VMware Tools Quiescing

VMware Tools is an optional set of drivers and utilities provided by VMware to enhance the performance of the guest operating system on a virtual machine and improve interaction between the guest and the host server. The tool also provides the ability to take quiesced snapshots of Windows guest OS in conjunction with Microsoft Volume Shadow Copy Service (VSS).

Phoenix 'Enable VMware tools quiescing' setting provides capability to enable or disable VMware tools quiescing if the tools are installed on the system. This functionality will ensure backups will still run by disabling the quiescence flag in case VMware tools are broken on your system.The quiesce setting is part of backup policy. If enabled, Phoenix will take an application consistent snapshot. If disabled or VMware tools not installed or running, the backup will still succeed with a crash-consistent snapshot. Restore points are not categorized under crash consistent and application consistent.

Note: By default, the Quiescing option is enabled in the Phoenix backup policy.

The following table illustrates the state of  VMware tools and the systems expected behavior: 

Enable VMware tools Quiescing  VMware tools installed  VMware tools running    VSS Service (Windows only)       Snapshot attempted
  No N/A     N/A N/A Crash-consistent - No Quiescing
Yes  No N/A N/A Crash-consistent - No Quiescing
Yes  Yes  No N/A Crash-consistent - No Quiescing

Yes 

Yes 

Yes 

Disabled    

  • If "VSS service startup type" option is set to Automatic/ Automatic(Delay)/Manual,  then VMtools starts the VSS service and does quiesced snapshot.
  • If "VSS service startup  type" option is disabled,  then snapshot operation will fail.
Yes  Yes  Yes  Enabled Application consistent - with Quiescing

 

Edit options for VMware Tools Quiescing

You can edit the VMware Tools Quiescing options when you:

  1. Configure virtual machines
  2. Reconfigure virtual machine
  3. Add a VMware backup policy
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