Change Block Tracking - HP StoreOnce D2D2500 Implementation Manual

Service Console based
This is for any size environment, but is only possible on ESX servers. vRanger can be installed inside a virtual or
physical machine. vRanger requests a snapshot of the virtual machine and then initiates direct copy of the virtual
machine from the ESX server console to the vRanger Repository. The backup data moves directly over the network to
the StoreOnce Backup System (Direct-to-Target) without going through the vRanger server. The Direct-to-Target
approach makes this architecture very scalable.
Figure 4: Service Console backup mode (Direct to Target)

Change block tracking

Change Block Tracking (CBT) is a VMware vSphere feature that tracks changes within the virtual machine disk
(VMDK) file. With CBT enabled, vRanger can efficiently identify the blocks that have changed since the last backup.
Identification of changed blocks is done by the VMware vStorage APIs for Data Protection (VADP), not by scanning
the VMDK file. Enabling CBT, typically results in shorter backup operations and reduced resource consumption on
network and storage elements. It is recommended to enable CBT for all virtual machines that support it. 2 There is a
slight performance overhead associated with enabling CBT, but it is minimal compared to the benefit it provides.
To enable or disable CBT right click on any virtual machine in the "My Inventory" pane of vRanger and select "Enable
Change Tracking" (or "Disable Change Tracking"), See Figure 5. Three small circles (Red-Blue-Green) indicate that
CBT is enabled.
Alternatively, CBT can be enabled in the vSphere client for each virtual machine, or you can use the Quest Power
GUI with the vRanger PowerPack to enable CBT for multiple virtual machines all at once.
2 CBT is supported by VMware for virtual machines running on ESX 4.0, ESXi 4.0 or later hosts (with virtual hardware 7). Virtual machines that are
created in ESX 3.5, ESXi 3.5, or below must be migrated to ESX 4.x or ESXi 4.x and Hardware Version 7 for CBT to be supported.
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