Backing Up Using NDMP

NDMP has the main advantage of speed over the NFS/CIFS protocols for backing up NAS filers. Note that NDMP is a control protocol, not a backup format. The NDMP backup format is arbitrary (implementation-specific) and defined individually by each storage platform vendor. Thus in general, an NDMP backup made on one vendor’s NAS system cannot be restored to a different vendor’s NAS.

NDMP can be used in 3 ways:

Filer to Server: Filer backing up across the LAN to your Bacula server.
Filer to Self: Filer backing up to an attached tape drive.
Filer to Filer: Filer backing up across the network to another filer’s tape drive.

At this time, the Bacula Enterprise NDMP Plugin supports only the Filer to Server mode. In this mode, Bacula encapsulates NDMP backup images inside the standard Bacula backup data stream, allowing it to be multiplexed with other backup streams and providing capabilities such as arbitrary (Bacula) storage device use, compression, checksum verification, etc. Inside the saved data stream that contains the NDMP stream, the actual NDMP data remains opaque (vendor specific format, sometimes proprietary).

When using NDMP provided by the NAS vendor, attributes such as ACLs are included in the backup stream and handled correctly by the NAS vendor on backup and restore. Determining which files should be saved is also part of the NAS vendor’s job, and Bacula has no way to ensure that all files will be protected with technologies such as our Accurate Mode.

Since Bacula does not implement the NDMP Direct Access Recovery (DAR) protocol (which is reputed to be very slow), doing a single file restore is possible via the Single Item Restore technique (use_hist option).

Restoring a single file with the NDMP Plugin without the Single Item Restore is possible by restoring the NDMP datastream to a local machine (same one that has the NDMP Plugin), then opening the resulting file. This requires to know the vendor data format and to have a program that can read it. Since it involves restoring the whole backup and then extracting the desired files, it isn’t very efficient.

An alternative, simple, and fast technique is to make use of file system snapshots made on the NAS to keep a history of file system states. These snapshots remain on the NAS box and can thus easily be accessed to restore individual files. In this manner, the NDMP backups are used as a disaster recovery mechanism only, rather than a means of restoring individual files.

In short, the best use of the NDMP Plugin is to protect the NAS from disaster situations, while using snapshots on the NAS box allows to recover files quickly on a daily basis.

Note

It is also possible to backup a particular snapshot with the NDMP Plugin.