Lingo Explained: 2-way NDMP vs. 3-way NDMP

NDMP or the Network Data Management Protocol can be used to secure data stored on NAS filers (such as NetApp, Hitachi HNAS, EMC Isilon, …). The protocol has been developed by NetApp, before it became an open standard maintained by Storage Network Industry Association (SNIA).

The initial goal to develop the NDMP protocol was to provide a standardized framework which can be used by any backup software, to avoid the need to deploy custom agents on the NAS filer. When no agents could be deployed – which occurred in most cases -, the backup admin was obligated to secure the data by using a proxy server which mounted the volumes by using the CIFS or NFS protocol.

In general we can say the NDMP protocol supports two data protection mechanisms: two-way – and three-way NDMP.

Two-way NDMP:
In a 2-way NDMP setup, the NAS filer is connected to a backup device (e.g. an LTO tape drive). The filer itself functions as a media agent and copies the data to a backup medium. Only management communication occurs over the network.

Three-way NDMP (sometimes also referred to as remote NDMP):
In a 3-way NDMP setup, all data is send to a media agent (e.g. Backup Exec Media Server) over the network. The media agent writes out the data on a backup device connected to the system.

Cluster-Aware Backup Extension:
When NetApp introduced Clustered Data OnTap (OnTap 8), the protocol got modified with a Cluster Aware Backup (CAB) extension to allow “node-scope two-way NDMP backups” as the volume could reside on any controller within the cluster. The main goal is to reduce the data traffic on the inter-cluster network and to speed up the backup – & recovery process.

What about restore when using two-way NDMP?
Before putting the NAS head in production, it’s always advised to perform some test restores with a special attention on “two-way NDMP restore” to ensure the local tape drive connection is used to recover the data. Refer to your backup software documentation to verify if this process is supported.

Port used by the NDMP protocol:
As NDMP is an open standard, all NDMP servers (= the storage appliance) use port 10000 by default.

Open question..
As NDMP is an open standard, I do expect you should be able to restore data backed-up by a Hitachi HNAS to a NetApp or Isilon and vice-versa.

Update 30-DEC-15: I stumbled onto the following thread, telling cross-vendor restore is not possible: “Each NAS vendor implements the NDMP protocol differently. EMC used to TAR their data, Isilon does something different, as does BlueArc. One NDMP backup may not be possible to be restored to different hardware, so in a way look at NDMP at proprietary.

Thanks for reading!

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