ATTO Technology 2500C - Manual (Page 20)

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ATTO Technology Inc. iPBridge Installation and Operation Manual
2.2 NDMP configuration provides backup
NDMP (Network Data Management Protocol) provides backup for network-attached storage (NAS)
devices. NAS devices are dedicated file servers and cannot host applications such as backup software.
NDMP defines a common agent to interface between any NAS device and any backup software program,
minimizing demand on network resources, and enabling local backups and disaster recovery.
Note
For NDMP-configured iPBridge 2500 models
only
The ATTO iPBridge 2500, using the NDMP
Version 4 Protocol Specification, 10/2001, (-
skardal-ndmp4.03.doc), allows you to back up
critical data locally using any combination of
network-attached servers, backup devices and
management applications from a central control,
without taxing network traffic, by separating the
data path and the control path.
How NDMP works
The NDMP protocol allows data backup and
restoration over telnet networks using file-level
commands, rather than block-level IO
instructions.
The typical NDMP setup includes
• a Data Service (usually disks)
• a Tape Service
• a client in control of the backup process called a
Data Management Application (DMA).
The DMA controls the NDMP session. There is a
master-slave relationship between the DMA and
the data/tape servers. The iPBridge 2500
implements the Tape Service, along with a SCSI
Service, to provide access to media changer
devices.
The iPBridge 2500 platform provides several
different types of management capability,
including telnet/FTP through the two GigE data
ports and an Ethernet 10/100/1000 management
port which may be used as a data port in the
iPBridge 2500 iSCSI-configured model, serial
CLI management, and standard bridge hardware
health checking.
A typical NDMP application involves a drive
array, a host computer and a tape library. the host
computer may be attached to the disk and tape
drives by any of several methods/technologies.
The iPBridge uses Ethernet and Internet
protocols.
The following example describes a host, Ethernet,
tape library configuration.
1 The DMA sends messages to the tape library’s
SCSI Server to pick the appropriate cartridge
and load it in the tape drive.
2 The DMA sends commands to the tape drive to
position the tape and configure the tape for
writing (block size, etc.).
3 The DMA opens a connection to the Data
Server to exchange backup information.
4 The DMA commands the Tape Server to
prepare to receive data.
5 The Tape Server responds with addressing
information.
6 The DMA passes the address to the Data
server.
7 The Data Server and Tape Server send data
directly to each other.
8 Metadata generated by the DMA is written to
tape to indicate the end of files, directories, path
names, etc., passed through to the tape server
between backup data transfers.
• NDMP uses a windowing mechanism in
which the Tape Server writes a portion of the
data, then pauses and waits for the DMA to
take charge. The DMA may start a new
window or write some Metadata.
• The DMA may also move the tape while the
transfer is paused. Once the DMA has
finished with the Metadata, a new window is
established and the transfer from the Data
Server to the Tape Server continues.
• The Data Server has no notification of the
Tape Server being paused, so it must rely on
the TCP stack to queue up data transferred
during the pause time, and to implement flow
control when queues are full.