BBB – Block Based Backup


NetWorker block based backups are high-performance backups that support all Microsoft Windows file systems except FAT 32.

During block based backups, the backup application scans a volume or a disk in a file system and backs up all the blocks that are in use in the file system. Block based backups use the following technologies:

· Use the Volume Shadow Copy Service (VSS) snapshot capability to create a consistent copy of the source volume for backup.

· Use the Virtual Hard Disk (VHDx), which is sparse, to write data to the target device.

Block based backups support only the following devices as target devices, where these devices are Client Direct enabled:

· Advanced File Type Devices (AFTDs)

· Data Domain devices

Block based incremental backups use the Change Block Tracking (CBT) driver to identify the changed blocks, and back up only the blocks that are changed.

You must install the latest recommended service packs and VSS patches.

Block based full and incremental backups are fast backups with reduced backup times because the backup process backs up only the occupied disk blocks and changed disk blocks, respectively. Block based backups can coexist with traditional backups.

Block based backups provide instant access to the backups. A block based backup enables you to mount the backup by using the same file system that you used to back up the data. For example, if the data that you backed up is NTFS, you can mount the block based backup by using NTFS.

A block based backup provides the following capabilities:

· Mounting of the backup as a file system

· Maximum of 38 incremental backups after a full backup

· Mounting of an incremental backup

· Sparse backup support

· Disk-based technology support

· Deduplication support

· Virtual full backups

· Synthetic full backups

· Incremental synthetic full backups

· Backups of volumes of 63 TB each

· Recoveries from Data Domain without using CIFS share

Limitations of block based backups

Block based backup does not support the following capabilities and configurations:

  • Non-Windows storage nodes
  • FAT32 file system
  • Backup levels 1 through 9
  • Synthetic full backups of mixed mode save sets
  • Cloning of incremental backups
  • Granular save sets at either the folder level or the file level, for example, D:data
  • Checkpoint restart
  • Staging
  • Standard NetWorker directives
  • The scanner command with the -i option for rebuilding indexes for block based backups
  • The nsrclone command with the -m option for migrating block based backup save sets to other volumes

A reboot is required upon installation of the block based backup feature. The reboot is required to initialize the write tracker (WT) Driver. The write tracking driver maintains a bitmap to track changes (write I/O requests) for every block based backup volume (Fulls and incrementals). The initialization of the write tracking driver enables the incremental backup functionality which is part of block based backups.

A full backup must be created initially. NetWorker uses VSS (Microsoft Volume Shadow Service) to create a Snapshot of the volume being backed up. It then checks the block based backup prerequisites to ensure a block based backup can be created. If the prereqs are satisfied, NetWorker creates the VHD container on the target device. It then obtains the list of used blocks in the volume and writes the blocks to the VHD container. After the blocks have been written it updates the MMDB with the VHD information to be used for subsequent incremental backups.

Incremental backups must be created on the same device and must go through a similar process as full backups. Incrementals use Microsoft VSS to create the snapshot. For each incremental a new bitmap is created using the write tracking driver. NetWorker also checks the prerequisites for each incremental. If the prerequisites are met it creates a VHD container on the target device. Finally, the list of changed blocks from the previous level full is obtained and written to the VHD container. For every incremental backup the write tracker driver is queried to get the previous bitmap that contains the list of changed blocks. Up to 38 incrementals can be created. After the 38th incremental a full backup is forced.

The backup scenarios and the recovery scenarios that block based backups support.

Table 104 Supported backup and recovery scenarios
Backup scenarios Recovery scenarios
· AFTD backups· Backups to Data Domain by using DD Boost

· Full backups

· Virtual full backups

· Synthetic full backups

· Incremental backups

· Incremental synthetic full backups

· Full backups and incremental backups intermixed with built-in provisions to anchor the incremental backups with an appropriate backup type

· File level recovery by mounting the backup image on a target host· Image/destructive recovery at the block level

· Image/destructive recovery from clones

· Windows Bare Metal Recovery (BMR) by using a WinPE image

CSV backups:

You can simultaneously see Cluster Shared Volumes (CSV) across all nodes. Block based backups support only full backups of CSV volumes, even in the case of a failover. If you try to perform an incremental backup, the backup shifts to a full backup with a warning message.For non-CSV volumes, if a failover happens af ter an incremental backup, the backup shifts to a full backup.

Manual backups or client-initiated backups:

Use the save command with the -z option to perform a client-initiated block based backup from the command line.

Ensure you meet the following requirements for a client-initiated backup:

  • The device must be Client Direct enabled.

You can provide a pool of Client Direct enabled devices by using the save command with the -b option.

  • The client-initiated block based backup supports the full level save sets that are defined only at the volume level.

Run the following command to clone the block based backup save sets:

nsrclone -b target_pool_name -S save_set_ID/clone_ID

Commands for performing file level recovery:

The following command mounts the backup and opens the command prompt at the mount point:

recover.exe -S ssid

Command for performing image/destructive recovery:

recover.exe -S ssid -r target_volume

Note: The WINDOWS ROLES AND FEATURES save set is not supported with BBB.

BBB:   Excluding files from Backup:

Both files and specific VSS writes are excluded from a block based backup.  Files are excluded using the Windows registry key FilesNotToBackup (HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\BackupRestore\FilesNotToBackup) according to Microsoft’s recommendations.  

Skip directives both global and local directives (.nsr) are NOT supported.


About Ahmad Sabry ElGendi
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4 Responses to BBB – Block Based Backup

  1. satya says:

    Why BBB are running as full backup, its common error with all servers and checked on EMC community there also a lot of people are asking same question.

    • Manjunath says:

      Manual backups are always full.
      In case of scheduled backups if the backups are always falling to full, the most likely issue is with the write tracking driver. Check if the driver is properly installed and initialized. Try restarting driver service –
      sc stop nsrbbb
      and then
      sc start nsrbbb.

      • Ge says:

        BBB always full is Resolved 9.0.1. Forces a Full because the nsrbbb driver cert is blocked upon boot.

        Question: Windows Roles and Features is no longer generated as a saveset. The only benefit of the Windows Roles and Features saveset is online recovery. Is the DR SaveSet inclusive roles in features upon BMR?

      • Hi,, Pardon me , I really don’t know so I can’t answer that question , I sugest to open SR with EMC or post this question in their community forum.

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