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NetBackup™ NAS Administrator's Guide

Last Published: 2025-03-18

Product(s): NetBackup & Alta Data Protection (11.0)

Accelerator forced rescan option

The policy schedules tab contains an option called Accelerator forced rescan. This option creates a checksum of the content of each file during backup. It uses the checksums for change detection. It provides safety by establishing a new baseline for the next Accelerator backup.

The Accelerator forced rescan option detects the following events:

The file's data changes, but the file's metadata does not change.
The file's metadata becomes corrupted, such that it does not indicate that the file has changed.
A malicious user or application changes the file's metadata such that it does not indicate that the file has changed.

Table: Required full-backup schedules for each Accelerator policy

Full backup schedules	Notes on schedule frequency
First schedule: Accelerator forced rescan disabled	Configure this schedule to run most of your Accelerator full backups.
Second schedule: Accelerator forced rescan enabled	Configure this schedule to run less often than the first full-backup schedule. For example: If the first full-backup schedule runs weekly, run the second schedule (with the Accelerator forced rescan option enabled) every few months. However, the best frequency for this schedule depends upon your environment. Note: If the policy has no schedule that enables the Accelerator forced rescan option, all full backups automatically enable that option and backup performance is reduced.

Full backup schedules

Notes on schedule frequency

First schedule:

Accelerator forced rescan disabled

Configure this schedule to run most of your Accelerator full backups.

Second schedule:

Accelerator forced rescan enabled

Configure this schedule to run less often than the first full-backup schedule.

For example: If the first full-backup schedule runs weekly, run the second schedule (with the Accelerator forced rescan option enabled) every few months. However, the best frequency for this schedule depends upon your environment.

Note:

If the policy has no schedule that enables the Accelerator forced rescan option, all full backups automatically enable that option and backup performance is reduced.

Note the following about the Accelerator forced rescan option:

The Accelerator forced rescan option is grayed out if the Use Accelerator option on the Attributes tab is not selected.
Because of the checksum processing on the backup host, this option reduces backup speed as compared to the Use Accelerator option on its own. The speed reduction depends on the backup host's configuration and its current processing load. If the backup host is busy with many jobs when Accelerator backup begins, checksum processing can reduce backup speed.