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Title
vRanger and Changed Block Tracking - (video) -
Description
Changed Block Tracking, is a feature of vSphere that identifies changed blocks within a VM’s disk and logs these blocks in a tracking file.
vRanger can utilize VMware's CBT to reduce backup/replication windows and resource usage for Incremental or differential passes of vRanger jobs.
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Cause
Traditionally vRanger will scan the entire VMDK for changed blocks. However when CBT is enabled, vRanger no longer needs to scan the VMDK for changes.
By skipping the manual scan for changed blocks and utilizing the CBT tracking file, the vRanger backup/replication window can be drastically reduced.
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Resolution
CBT is not enabled by default on a VM.
NOTE: Enabling CBT does require a minimal amount of additional resources on the ESX(i) host. Also, CBT is limited to VMDK’s & vRDM‘s.
Requirements:
- vSphere ESX(i) 4+
- Virtual HW 7+
To Enable CBT through vRanger:
- Locate the VM in the My inventory Section.
- Right click on the VM and select "Enable Change Tracking"
- The VM must go through a stun/unstun cycle to activate changed block tracking. Create and remove a snapshot on the VM to accomplish this.
CBT enabled VM's will have a Changed Tracking Icon (3 blocks) next to the VM in the My Inventory Section.