NDMP or Network Data Management Protocol

An open protocol for enterprise-wide, network-based data management such as backup and recovery. NDMP is a control protocol used to control the NDMP services participating in the session. NDMP specifies the format and means of transmission of messages and payload data between a DMA and an NDMP server, and between two NDMP servers. NDMP is increasingly being used for replication/copying of data in primary or secondary storage systems.

DMA or Data Management Application

The Data Management Application (DMA) that controls the NDMP session. In NDMP there is a master-slave relationship. The DMA is the session master; the NDMP services are the slaves. In NDMP versions 1, 2, and 3 the term “NDMP client” was used instead of “DMA.”

NDMP Host

The host computer system that executes the NDMP Server application. Data is backed up from the NDMP host to either a local tape drive or to a backup device on a remote NDMP host.

NDMP Service

The state machine on the NDMP host accessed with the Internet protocol and controlled using the NDMP protocol. This term is used independently of implementation. There are two types of NDMP Services: Data Service and Tape Service.

NDMP Server

An instance of one or more distinct NDMP services controlled by a single NDMP control connection. Thus a Data/Tape/SCSI Server is an NDMP Server providing Data, Tape, and SCSI services.

Primary Storage System

A storage system that stores live or “in production” data on an active file system. Examples are direct or SAN attached storage in application servers, or dedicated storage appliances such as filers. A primary storage system hosts an NDMP data service.

Secondary Storage System

A storage system used for archiving or data protection. Examples are application servers with direct attached tape drives, libraries or robots, or dedicated network attached archiving/data protection appliances. A secondary storage system hosts an NDMP tape service and often a SCSI service.

Backup or Backup Operation

Copying selected data from primary storage to secondary storage.

Recovery or Recovery Operation

Copying selected data from primary storage to secondary storage.

Control Connection

A bi-directional TCP/IP connection that carries XDR encoded NDMP messages between the DMA and the NDMP Server.

Data Connection

The connection between the two NDMP Servers that carry the data stream. The data connection in NDMP is either an NDMP interprocess communication mechanism (for local operations) or a TCP/IP connection (for 3-way operations).

1. Design and Implementation

Technical details

We use the Network Data Management Protocol specifications for backup                                                                                                                                        and recovery. The Network Data Management Protocol (NDMP) addresses the user’s need for centralized control of enterprise wide network data management while minimizing network traffic. NDMP ensures interoperability between different file servers and backup solutions, significantly simplifying the data management process.

Architecture for backup & recovery

Implementation Details

The implementation of backup and recovery is according to the specifications of Network Data Management Protocol (NDMP) v4. There is a third party agent i.e. DMA which controls the source i.e. the Data server and the destination i.e. File Server. It does the entire job of connection establishment and the negotiation between the source and the destination. The DMA issues the commands to the Servers through the control connections while the data flows via the data connection between the servers. The messages to and from the DMA are XDR encoded to make them platform independent. This solves the problem of backup on heterogeneous environment.

The checkpoints are put on to the data which is backed up. They help in recovering from a failure during backup and recovery. These checkpoints are maintained by the file server and then the log is sent to the DMA. In case of failure, DMA refers to this log and then starts the process from where it failed. Hence saving time and space. Different type of backups supported would include, plain, differential and incremental.