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Learn how Changed Block Tracking (CBT) and Active Block Mapping (ABM) optimize image-based backup processes, reducing overhead and improving efficiency. Explore their individual and combined impacts on performance.
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vRanger Pro 4.5 CBT and ABM
Image-Based Backup: Activities Impacting Performance • 1: Scanning • 3: Writing 2: Reading 0 0 0 0 0
How CBT and ABM work together A typical disk layout, before 1st backup 0 0 0 0 Active Block Unallocated Block 0 Zero Block 0 Changed Block Deleted Data
Fulls: without CBT or ABM • All blocks must be scanned and read • Unallocated and zero blocks are both read as zeros • vRanger engine removes all “whitespace” on writes Scan and Read Write 0 0 0 0 0 0 0 Active Block Unallocated Block 0 0 Zero Block 0 Changed Block Deleted Data
Fulls: with CBT • Does not scan unallocated blocks • Zeros and deleted blocks are scanned and read • vRangerengine removes “whitespace” on writes Scan and Read Write 0 0 0 0 0 0 0 0 0 0 Active Block Unallocated Block 0 0 0 0 Zero Block 0 Changed Block Deleted Data
Fulls: with ABM • Does not scan zero nor deleted blocks • Unallocated blocks are scanned and read • vRanger engine removes un-allocated “whitespace” Scan and Read Write Active Block Unallocated Block Zero Block 0 Changed Block Deleted Data
Fulls: with Both ABM and CBT • Scans the minimum set of blocks: no zero nor unallocated whitespace, no deleted blocks Write Scan and Read Active Block Unallocated Block Zero Block 0 Changed Block Deleted Data
How CBT and ABM work together A typical disk layout, after 1st backup 0 0 0 Active Block Unallocated Block 0 Zero Block 0 Changed Block Deleted Data
Incrementals: without ABM or CBT • All blocks are scanned • Only changed blocks are read • vRanger engine removes “whitespace” Scan and Read Write 0 0 0 Active Block Unallocated Block 0 Zero Block 0 Changed Block Deleted Data
Incrementals: with CBT • Changed blocks are “presented” to vRanger by vSphere API • No scanning necessary • Only changed blocks are read and written From vStorage API Read and Write Active Block Unallocated Block Zero Block 0 Changed Block Deleted Data
Incrementals: with ABM • Active blocks are presented to vRanger by Windows NTFS • Scanning includes only active and unallocated blocks (zero and inactive blocks are not included in the scan) • Only changed, active blocks are read and written Scanned Read and Written Active Block Unallocated Block Zero Block 0 Changed Block Deleted Data
Incrementals: Both ABM and CBT together • No scanning • Only active and changed blocks are read and written From vStorage API Read and Written Active Block Unallocated Block Zero Block 0 Changed Block Deleted Data