Alternatives to NDMP [Part 1]

I got a great question from a person considering different approaches to the backup of a NAS – they asked about alternatives to NDMP for backing up a NAS.  Because we service the SMB/SME space, we get asked this a lot – and yet a quick Google search didn’t turn up a lot – so I thought it was worth posting.

Unitrends supports not only heterogeneous platforms and operating systems but also heterogeneous storage types.  These storage types include DAS (Direct Attached Storage), SANs (Storage Attached Networks), and NASs (Network Attached Storage.)  DAS support and SAN support are a function of the platform and the operating system residing upon that platform; in other words, the DAS and SAN storage is used as a low-level “block-level” device with a “personality” completely driven by the platform and operating system using the storage.  NAS support is different; NAS is a “file-level” device which is accessed as a free-standing file system.

Protecting a NAS device is more complicated than protecting a DAS or SAN device because it in essence operates as an embedded server offering higher-level file services.  There are primarily three mechanisms typically employed to protect NAS devices:

Client-Based NAS Attach: The NAS is attached to the client (which is the customer’s computer in this case), and then the client is attached to the backup server.  The protocol used to communicate between the NAS and client, and between the client and the backup service, is either CIFS or NFS.  CIFS (Common Internet File System) is a protocol originally developed by Microsoft while NFS (Network File System) is a protocol originally developed by Sun Microsystems.  The primary disadvantages of this approach is that performance is decreased because data must be copied from the NAS to the client and then from the client to the backup server.  Unfortunately, the client suffers performance degradation due to the intermediate copying of data.

Direct NAS Attach: The NAS is attached to both the client and the backup server.  The protocol used to communicate is CIFS or NFS.  The primary advantage of this approach that the disadvantages to the client-based NAS approach are negated: performance is increased and the client’s performance is not affected.

NDMP (Network Data Management Protocol): A protocol invented by NetApp and Legato specifically for transport of data between NASs and tape devices.  Just as in direct NAS attach, the NAS is attached directly to both the client and the backup server.  This approach offers the same performance improvement as the direct NAS attach method.

In the next few days, I’ll publish part 2 of this series in which I’ll go through a more detailed discussion of the advantages and disadvantages of these three approaches.


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