Learning about NDMP services on the storage system

What NDMP is

The Network Data Management Protocol (NDMP) is a standardized protocol for controlling backup, recovery, and other transfers of data between primary and secondary storage devices such as storage systems and tape libraries.

By enabling NDMP protocol support on a storage system, you enable that storage system to carry out communications with NDMP-enabled commercial network-attached backup applications (also called Data Management Applications or DMAs), data servers, and tape servers participating in backup or recovery operations.

NDMP also provides low-level control of tape devices and medium changers.

Note
You can use the following snapmirror commands when using NDMP:

abort
help
retrieve
status
store
use

See the Online Backup and Recovery Guide for information on the snapmirror command.

Advantages of NDMP

Data ONTAP NDMP backup and recovery operations use the same dump and restore services described in the chapters about data backup to tape and data restoration from tape. However, accessing these data protection services through backup applications that support NDMP offers a number of advantages.

NDMP backup applications provide sophisticated scheduling of data protection operations across multiple storage systems. They also provide media management and tape inventory management services to eliminate or minimize manual tape handling during data protection operations.
NDMP backup applications support data cataloging services that simplify the process of locating specific recovery data. Direct Access Recovery (DAR) optimizes the access of specific data from large backup tape sets.
NDMP supports multiple topology configurations, allowing efficient sharing of secondary storage (tape library) resources through the use of three-way network data connections. NDMP backup applications typically provide user-friendly interfaces that simplify the management of data protection services.

Some common NDMP tape backup topologies

NDMP supports a number of topologies and configurations between backup applications and storage systems or other NDMP servers providing data (file systems) and tape services.

Storage system-to-local-tape

In the simplest configuration, a backup application backs up data from a storage system to a tape subsystem attached to the storage system. The NDMP control connection exists across the network boundary. The NDMP data connection that exists within the storage system between the data and tape services is called an NDMP local configuration.

Storage system-to-storage system-to-tape

A backup application can also back up data from a storage system to a tape library (a medium changer with one or more tape drives) attached to another storage system. In this case, the NDMP data connection between the data and tape services is provided by a TCP/IP network connection. This is referred to as an NDMP three-way storage system-to-storage system configuration.

Storage system-to-network attached tape library

NDMP-enabled tape libraries provide a variation of the three-way configuration. In this case, the tape library attaches directly to the TCP/IP network and communicates with the backup application and the storage system through an internal NDMP server.

Storage system-to-data-server-to-tape or data-server-to-storage system-to-tape

NDMP also supports storage system-to-data-server and data-server-to-storage system three-way configurations, although these variants are less widely deployed. Storage system-to-server allows storage system data to be backed up to a tape library attached to the backup application host or to another data server system. The server-to-storage system configuration allows server data to be backed up to a storage system-attached tape library.

NDMP security

Data ONTAP provides features for preventing or monitoring for unauthorized use of NDMP connections to your storage system. You can restrict the set of backup application hosts permitted to start NDMP sessions on a storage system. You can specify the authentication method to use (text or challenge) in order to allow NDMP requests. You can enable or disable monitoring of NDMP connection requests.

Data ONTAP also generates an NDMP-specific passwords for administers who do not have root privilege on the target storage system.

Considerations when using NDMP

Take the following considerations into account when starting NDMP service on your storage system:

Data ONTAP supports a maximum of 16 concurrent backup and/or restore operations. The maximum includes backups initiated by NDMP as well as by the storage system's dump and/or restore command.
NDMP supports a maximum of 128 concurrent sessions on NearStore systems, and 40 on other systems.
NDMP backup applications require specification of a target system password. To enable successful authentication by NDMP services on the storage system, you must use either the storage system's root password or, to authenticate a non-root user administrator, a system-generated NDMP-specific password.
NDMP services optionally generate file history data at the request of NDMP backup applications. File history is used by backup applications to enable optimized recovery of selected subsets of data from a backup image. File history generation and processing is time-consuming and CPU-intensive for both the storage system and the backup application. If your data protection needs are limited to disaster recovery, where the entire backup image will be recovered, you may want to disable file history generation to reduce backup times. See your backup application documentation to determine if it is possible to disable NDMP file history generation.
If enhanced Direct Access Restore (DAR) functionality is enabled, an offset map is generated at backup time. The processing required to generate the offset map is directly related to the number of files that need to be processed and can result in a significant impact to performance if a large number of small files are backed up. See Enabling or disabling enhanced DAR functionality.
NDMP does not support Unicode format. If you use a third-party tool to back up a storage system using the Unicode directory format, the NDMP primary storage displays the file names in the NDMP file history database in two ways:
- If possible, the storage system replaces the Unicode format with the NFS character set.
- If the storage system cannot replace the Unicode format with the NFS character set, the NDMP client displays the file names as: XXXXXXX, where XXXXXXX is a character string.
Because NDMP uses the restore command to recover files, you can use NDMP to restore files with correct file names regardless of how the client displays the file names in the NDMP file history database.