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To put NAS backups into perspective, you must first look at a little history. Back when all hard-disk storage was directly attached to the computer using it, backups were relatively straightforward; you installed data backup software that transmitted data to a directly attached tape device.
As servers multiplied and environments grew larger, it became more manageable to transmit data over the network to a server that managed all the backups and the required storage media. This remained a common backup method regardless of whether the hard-disk storage was attached to the system via a SCSI cable or Fibre Channel. However, with the popularity of NAS appliances, you should take a fresh look at NAS backup strategies.
NAS appliances look like scalable file servers, but they work differently. For one, these appliances run proprietary operating systems optimized for storage performance. For that reason, you cannot install the usual backup software agents on a NAS device.
Unlike Microsoft Windows, Unix, Linux or macOS-based servers, which are widely supported by many backup software vendors, NAS devices require a different approach. Here, we review four common NAS backup strategies.
Traditional network-based backup
A traditional network-based backup relies on backup agents installed on all the servers that access storage on a NAS device, and the data is sent to a backup server across the network. This is essentially business as usual in terms of client-server backups, which is why it is referred to as a traditional network-based backup in this context.
While this approach requires no special changes to the environment, it is not the most effective of the NAS backup strategies. For one, it increases network traffic because data must travel on the network from the NAS devices to the client and again from the client to the backup server. In addition, in cases where a NAS device is used as a file server shared by multiple systems, the backup software on each system can create multiple backup copies of the same files.
You can deal with this issue by designating a single system as a backup proxy for the entire NAS device. In this context, using a proxy means that a single system acting as a backup client handles the backup for the entire NAS device. However, this method is ineffective when NAS devices are also used to store application-specific data, such as databases that require application awareness or shutdowns to generate useable backups.
The Network Data Management Protocol (NDMP) is a protocol that was created specifically for NAS device backups. NDMP allows a NAS device to send data directly to a tape device or backup server across the network without the need for backup client intervention. In other words, the backup server communicates directly with the NAS appliance, indicating which storage device data can be sent to for backup. Most mainstream backup software packages, such as those from Commvault, Dell EMC, IBM and Veritas, support NDMP and offer various levels of integration and functionality.
However, NDMP backups are best-suited for file data. Other than Oracle Secure Backup, which is NDMP-capable, NDMP backups are not well-integrated with database applications such as Microsoft Exchange, SQL, Db2, etc., which need to be aware that a backup is taking place to ensure consistency. While you can achieve this with custom scripting, it typically requires applications to be shut down temporarily and introduces potential support challenges, as with most custom products.
NAS-based data replication
Data replication between NAS devices offers, by far, the most advanced features and the best integration with applications. Vendors use a combination of local and remote replication, as well as application-specific modules, to provide NAS data protection. Examples of this technology include the NetApp Snap suite and Dell EMC SyncIQ.
The NetApp data protection capabilities include snapshots for local, block-level and point-in-time copies; SnapVault for local or remote block-level incremental backup; and SnapMirror for local or remote data replication. The suite also includes the SnapManager data management capability to automate and simplify the backup of application data, such as SQL, Exchange, Oracle, etc., which requires application-aware backups.
With Dell EMC Isilon scale-out NAS, the user can manage petabytes of backup storage within a single system. Isilon SyncIQ is an application that enables the management and automation of data replication.
Both vendors have also integrated data deduplication technology into their products to help reduce the footprint of backup data.
Online data backup
Some NAS device vendors that focus mostly on the SMB market have combined online data backup and cloud storage services. Examples of cloud storage tools include Ctera Networks' CloudPlug and Netgear's ReadyNAS Vault. Their main differentiator is the ability to provide a simple backup and disaster recovery product to their clients.
Datto NAS is a network-attached storage product that connects to Datto Inc.'s cloud. Customers can replicate NAS snapshots to Datto Cloud for backup.
A more recent entrant into the data protection market, Igneous Systems, provides backup support for NAS providers. Igneous backs up data to its fully managed appliance, and customers can also tier data up to the public cloud.
Each one of these NAS backup strategies comes with a price, but can also meet specific recovery requirements. Highly automated, block-level replication technologies will support much tighter recovery time objectives and recovery point objectives than a client-based, network backup-to-tape platform could. As always, the approach and associated cost should be justified by the recovery requirements.
This article was originally published in 2010 and updated in April 2019.