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NetBackup™ NAS Administrator's Guide

Last Published: 2025-08-12

Product(s): NetBackup (11.0.0.1)

About NetBackup Accelerator for NDMP

Note:

Currently only NetApp filers and Isilon filers are supported with the NetBackup Accelerator for NDMP option. (See the NetBackup Compatibility List for all Versions for the most recent list of supported versions of each NAS vendor.)

For NetApp filers, Accelerator for NDMP supports only the DUMP format. Consult your NetApp documentation for specific details about its DUMP format.

NetBackup's Accelerator option makes NDMP backups for NetApp and Isilon filers run faster than normal NDMP backups. NetBackup Accelerator increases the speed of full backups by using the filer's change detection techniques to identify the modifications that occurred since the last backup. After an initial full backup that protects all data from the filer, NetBackup Accelerator backs up only the changed data from the filer to the media server. The media server combines the changed data with any previous backup images to create a new full backup image; if a file or portion of a file is already in storage and has not been changed, the media server uses the copy in storage rather than reading it from the filer to complete the backup image. The end result is a faster NetBackup NDMP backup.

Note:

For NetApp filers, you can expect to see Accelerator optimization in both full backups (regular and forced rescan) and incremental backups. For Isilon filers, you can expect to see Accelerator optimization only in full backups (regular - not forced rescan).

Accelerator for NDMP has the following advantages:

Supports all NetBackup NDMP features, such as replication, DAR restores, and multiplexing.
Creates a compact backup stream that uses less network bandwidth between the filer and NetBackup servers.
Reduces the I/O and CPU overhead on the media server.

To configure Accelerator for NDMP, select the Use Accelerator check box that is found on the NDMP policy Attributes tab. No change to the filer is required.

Note:

For Isilon filers only, note the following behaviors with environmental variables:

With Isilon filers, if you set the HIST environment variable in a NetBackup NDMP backup policy with Accelerator enabled, you may specify only the value D (that is, SET HIST=D). D specifies a directory/node file history format. If you specify any other value for the HIST variable, NetBackup generates a message that asks you to change the value to D. If you do not use a HIST variable in the policy, the backup should complete successfully.

If you change any of the variables in a NetBackup NDMP backup policy with Accelerator enabled, the Accelerator optimization will be 0% until you run a second full backup with the same variables. When the policy's variables change, a new baseline image is created with the first full backup. You will see Accelerator optimization only after the second full backup with the same variables.

More information about environmental variables in NDMP policies is available:

See About environment variables in the backup selections list.

Note:

If you include the smtape environment variable for NetApp filers in an NDMP backup policy, no optimization is seen with Accelerator for NDMP enabled. The smtape environment variable always backs up an entire volume as if it is a full backup of a single file. Consult your NetApp filer documentation for specific details about smtape. See About NAS appliances support. for information about smtape in a NetBackup backup policy is available in the NetApp section.

If your NDMP policies include combinations of filers from NetApp, Isilon, and filers from other vendors, only the NetApp and Isilon filers use the Accelerator option. Messages in the job details identify which filers use the Accelerator option and when the option is used. More information about these job detail messages is available:

See Accelerator messages in the NDMP backup job details log.

Note:

Unlike non-accelerated NDMP backups, accelerated NDMP backups do not use NDMP dump levels 0-9 to determine changed files. Instead, BASE_DATE and DUMP_DATE are used to determine changed files. BASE_DATE provides the timestamp of the most recent full or incremental backup. DUMP_DATE provides the timestamp of the currently running backup. Only the data that has changed between the BASE_DATE and the DUMP_DATE is backed up when Accelerator for NDMP is enabled.

Dump level messages from the filer continue to be included in the job detail log. However, the message please ignore references to LEVEL in future messages also appears in the job details as a reminder that dump levels are not used with Accelerator for NDMP.

How Accelerator works with NDMP backups:

First full backup with Accelerator
The first full NDMP backup job with the Accelerator option enabled is similar to a normal full backup. It may run slightly longer than a non-Accelerator backup. It backs up all of the data from the filer, provides a baseline backup image, and creates an initial track log.
Note:
If you first enable Accelerator when the next scheduled backup is an incremental backup, NetBackup does not automatically trigger a full backup image, as is the case with NetBackup Accelerator for non-NDMP policies. With Accelerator for NDMP, incremental backups continue to run as scheduled. An initial track log is also created after the Use Accelerator option is enabled, and with NetApp filers, you should see faster incremental backups. The next full backup runs only when it is scheduled.
Incremental backups with Accelerator
Subsequent incremental backup jobs back up only the data that changed since the last backup job.
Next full backups with Accelerator
Subsequent full backup jobs back up only the data that changed since the last backup job. The track log is used to determine what data can be included from previous backups, including the previous full backup and all of the incremental backups that follow it. NetBackup then creates a full backup image that includes all of the filer's data.
Forced rescan full backups with Accelerator
The Accelerator forced rescan option provides a safety net by establishing a new baseline for the next Accelerator backup. When you include this option, which is found on the policy's Schedules tab, all the data on the filer is backed up. This backup is similar to the first full backup with Accelerator; it provides a new baseline for the backups that follow. If you set up a weekly full backup schedule with the Use Accelerator option, you can supplement the policy with another schedule that enables Accelerator forced rescan. You can set the schedule to run every 6 months or whenever it is appropriate for your environment. With NetApp filers, expect backups with Accelerator forced rescan to run slightly longer than accelerated full backups. With Isilon filers, backups with Accelerator forced rescan may run as longer as a first full backup with Accelerator. More information about these options is available:
- See Attributes tab options for an NDMP policy.
- See Schedules tab options for an NDMP policy with Accelerator for NDMP enabled.