About NDMP multiplexing
NDMP multiplexing concurrently writes multiple backup streams to the same tape storage device from the same client or different clients. NDMP multiplexing supports only remote NDMP and improves overall NetBackup performance by better using tape storage devices. State-of-the-art tape storage devices can typically stream data faster than client agents can create backup streams. Therefore multiple data streams can be sent to and effectively processed by a given tape storage unit.
A network-attached storage (NAS) device with an NDMP server is an agent that produces a backup stream that is similar to a NetBackup client. Multiplexing is desired for NDMP backups because NAS devices are limited in the rate at which they create backup streams. These backup streams are often much slower than the tape storage device consuming and writing the stream.
NDMP multiplexing provides the following benefits:
Several backups can be run at the same time writing to the same tape. This process can reduce the need for many tape devices.
Backup time is reduced by writing concurrent backups to a single tape storage device.
Many tape storage devices require that data is streamed to them at high transfer rates. When data is not streamed fast enough, they do not work efficiently and are subject to possible excessive wear.
Consider the following general items when implementing NDMP multiplexing:
Only media manager tape storage units can be used for NDMP multiplexing.
Multiplexing of NDMP backups and restores supports only remote NDMP. The remote NDMP processes backup streams by going through the media server.
NDMP local and NDMP three-way backups and restores are not supported for NDMP multiplexing. Each method processes backup streams without going through the media server.
Synthetic backups are not supported.
Only tape devices are supported.
Disk storage devices are not supported.
A mix of NDMP and non-NDMP backups can be present in the same MPX backup group.
File and directory DAR are allowed.
NDMP multiplexing works with both VTL and PTL. However, VTL users typically do not use NDMP multiplexing because they can add more virtual tape devices to accommodate additional streams.
For NDMP multiplexed backups the storage unit and policy schedule multiplex value must be set to a value greater than one.