Backup policies specify virtual machine backup options, the schedule window, and retention policies in this validated design.

Options for Virtual Machine Backup

VADP provides the following options for a virtual machine backup:

Network Block Device (NBD)

Transfers virtual machine data across the network so that VADP-compatible solution can perform the backups.

  • The performance of the virtual machine network traffic might be lower.

  • NBD takes a quiesced snapshot. As a result, it might interrupt the I/O operations of the virtual machine to swap the .vmdk file or consolidate the data after the backup is complete.

  • The time to complete the virtual machine backup might be longer than the backup window.

  • NBD does not work in multi-writer disk mode.

Protection Agent Inside Guest OS

Provides backup of certain applications that are running in the guest operating system by using an installed backup agent.

  • Enables application-consistent backup and recovery with Microsoft SQL Server, Microsoft SharePoint, and Microsoft Exchange support.

  • Provides more granularity and flexibility to restore on the file level.

Table 1. Design Decisions on Virtual Machine Transport Mode

Decision ID

Design Decision

Design Justification

Design Implication


Use HotAdd to back up virtual machines.

HotAdd optimizes and speeds up virtual machine backups, and does not impact the vSphere management network.

All ESXi hosts must have the same visibility of the virtual machine datastores.

Schedule Window

Even though VADP uses the Changed Block Tracking technology to optimize the backup data, to avoid any business impact, do not use a backup window when the production storage is in high demand.

Table 2. Design Decisions on Backup Schedule

Decision ID

Design Decision

Design Justification

Design Implication


Schedule daily backups.

You can recover virtual machine data that is at most a day old.

You lose data that changed since the last backup 24 hours ago.


Schedule backups outside the production peak times.

Backups occur when the system is under the lowest load. Make sure that backups are completed in the shortest time possible with the smallest risk of errors.

There may be limited non-peak time to complete backups. Backup duration will be impacte dy storage I/O throughput.

Retention Policies

Retention policies are properties of a backup job. If you group virtual machines by business priority, you can set the retention requirements according to the business priority.

Table 3. Design Decisions on Backup Retention Policies

Decision ID

Design Decision

Design Justification

Design Implication


Retain backups for at least 3 days.

Keeping 3 days of backups enables administrators to restore the management applications to a state within the last 72 hours.

Depending on the rate of change in virtual machines, backup retention policy can increase the storage target size.