The Saviour of NAS Backups



Remember a few months back that I discussed the different methods of backing up a NAS.

The biggest problem that was highlighted in that article was that full backups of a NAS using NDMP are a real pain.  Backup windows extend beyond the allowed amount of time because the NAS storage scales but NDMP backups don’t!

The options for protecting a NAS that I highlighted were:

1. CIFS / NFS mount the drives to a proxy.
2. NDMP backups
3. 3rd Party integration (e.g. Tivoli snapdiff )
4. No traditional backup – use the force (of the NAS) – snapshots and replication

I concluded that NDMP backups are so painful that the easiest way to protect the NAS is to use snapshots, however that presents problems too!  Snapshots in my opinion are not really a backup as you are not getting the data out of the original systems into a safe location.  You are also locked into the vendor for your storage and protection strategy.

The 5th way!!

There is another option though.  This allows you to do NDMP backups but more efficiently so they fit in your backup window. This method performs a sub-file incremental forever backup of your NAS.

The solution is provided by EMC’s Avamar product with the additional NDMP Accelerator node.  The Accelerator node is essentially an NDMP target device that receives the NDMP backup stream, dis-assembles it, chunks, hashes and dudupes it before sending it to the Avamar Data Store.

Bits you need:

1. NAS (either EMC VNX , VNXe, or NetApp)
2. Avamar Data store. This consists of a utility node which catalogs the backups and holds scheduling info and data nodes that (weirdly) hold the data
3. Avamar NDMP Accelerator


The Avamar Data Store sends and instruction to the NAS to perform an INCREMENTAL NDMP backup. The device that is used to send the NDMP stream to is the Accelerator node. This then Chunks, Hashes, Compresses and dedupes the data using the Avamar source based technique.  Once this process is done the resulting unique data is sent from the Accelerator to the Data Store.

Using the figures in the picture above the data moved is hugely reduced.  A comparison of traditional backups vs Avamar is made below:

Type Sent from NAS Received by Target device

Traditional NDMP backups to tape

Full Backup 1TB 1TB
Incremental 100GB 100GB

Avamar NDMP Accelerator Backups

Full Backup (1st Incr) 1TB 1TB (maybe reduced by compression)
Incremental 100GB 3-10GB

Avamar will always present these incremental backups as though they were full backups.  This means there isn’t the need to roll forward multiple incremental backups.  Avamar will just pull back the entire volume as it looked at the point in time the backup was taken.

So in summary then, the way you should backup a NAS but couldn’t in the past has just become possible!

See this article for more info – Evaluator Group on Avamar NAS backups