About NDMP backups

NDMP devices are protected at the volume level. When running an on-demand backup or creating a backup schedule for an NDMP client, you must specify the volume(s) you wish to protect. Each volume is protected individually.

The protocol limits the number of incremental backups between successful full backups to 9. If your backup schedule has more than 9 incrementals between each full backup, incrementals are automatically promoted to differentials as needed and then jobs resume as scheduled. For more information, see Automatic promotions of NDMP Incremental backups .

Note: Enterprise backups are not supported for NDMP clients.

Automatic promotions of NDMP Incremental backups

NDMP limits the number of incrementals that can occur between fulls to 9. This limitation is enforced by assigning and tracking levels of each backup type. It does so in the following way:

     Fulls are always counted as level ‘0.’

     Differentials are always counted as level ‘1.’

     Incrementals are counted by increasing the previous backup’s level by 1. These can be counted as levels 1-9, with nine being the maximum level allowed by the protocol.

Automatic promotion for schedules

For schedules, the NDMP level assignments described above mean scheduled incremental backups are automatically promoted to differentials if there is already a level-9 backup in that volume’s current backup group. The promotion to a differential resets the level to one. After the automatic promotion, the schedule resumes running the jobs as expected.

The graphic below demonstrates the automatic promotion behavior for schedules with more than 9 incrementals between each full backup. The schedule below has one full on the first of each month and daily incrementals in between.

Promotion1.png

As you see, the regularly scheduled full runs followed by 9 incrementals. Then a scheduled incremental is automatically promoted to a differential, resetting the level to 1, and resumes running as scheduled with automatic promotions each time the maximum level of 9 is reached.

Note: Only 8 incrementals run between automatically promoted differentials because the count starts from 1 rather than 0 (as it does with full backups).

One-time incremental backups and automatic promotion

On-demand incremental backups also affect the backup level for the volume. If you attempt to run a one-time incremental backup and the backup level is less than 9, the job is queued and the backup level of the group is increased by one. However, if the volume’s backup level is already 9, the job is not queued. Instead you are notified that you have reached the maximum limit of consecutive incremental backups for this volume and a full must be run.

The graphic below demonstrates how one-time incrementals can affect the automatic promotions within an existing schedule. In this case, the schedule is the same as example one, but an on-demand incremental backup is also run on the 6th day.

Promotion2.png

Similar to the first example, the regularly scheduled full runs followed by 9 incrementals. However, on day 6 the level is increased by a total of 2: first by the regularly scheduled incremental and then by the on-demand incremental backup. This results in the automatic promotion to a differential occurring one day earlier than it did in the first example. The schedule then resumes running as scheduled with automatic promotions each time the maximum level of 9 is reached.

Note: Only 8 incrementals run between automatically promoted differentials because the count starts from 1 rather than 0 (as it does with full backups).

Differential backups and automatic promotion

Because differential backups are always counted as level 1, they do not have the same limitations as incremental backups. Any number of differentials can be run between successful full backups of an NDMP volume.