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Full backup and restore of Thick Provisioned, Eager Zeroed disks backs up all blocks, including zeroed-out blocks. Example log from a full backup of an empty thick-provisioned disk 2025-11-03T23:07:10Z INFO: [@(#) Build number: 90] "Label": "Hard disk 1", 2025-11-03T23:07:10Z INFO: [@(#) Build number: 90] "State": "Success", 2025-11-03T23:07:10Z INFO: [@(#) Build number: 90] "Description": "Success", 2025-11-03T23:07:10Z INFO: [@(#) Build number: 90] "VddkTransportMode": "hotadd", 2025-11-03T23:07:10Z INFO: [@(#) Build number: 90] "Statistics": { 2025-11-03T23:07:10Z INFO: [@(#) Build number: 90] "ProvisionedBytes": 4294967296, 2025-11-03T23:07:10Z INFO: [@(#) Build number: 90] "UsedBytes": 0, 2025-11-03T23:07:10Z INFO: [@(#) Build number: 90] "ChangedBytes": 0, 2025-11-03T23:07:10Z INFO: [@(#) Build number: 90] "BytesMoved": 0, 2025-11-03T23:07:10Z INFO: [@(#) Build number: 90] "BytesToMove": 0, 2025-11-03T23:07:10Z INFO: [@(#) Build number: 90] "SecondsToRead": 0, 2025-11-03T23:07:10Z INFO: [@(#) Build number: 90] "SecondsToWrite": 0, 2025-11-03T23:07:10Z INFO: [@(#) Build number: 90] "SecondsTaken": 29,
This is expected behavior. VMware vSphere Storage APIs - Data Protection (VADP) APIs and Virtual Disk Development Kit (VDDK) APIs used by vProxy during full backups do not differentiate unused blocks from zeroed-out blocks on thick provisioned disks.
NetWorker is functioning as designed: During Full backups , all blocks on thick provisioned disks are backed up and restored. This can increase backup and restore time, but the impact is minimal because DD Boost reduces network traffic for unused blocks. Incremental backups use Change Block Tracking (CBT) , so zeroed blocks are ignored until data is written. Thick Provisioned, Eager Zeroed disks allocate all space upfront and zero out blocks during provisioning. Thin Provisioned disks only allocate space as data is written, reducing backup size and time.
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