How to Choose Network Attached Storage

A network-attached storage (NAS) device is a server that is dedicated for file sharing. NAS does not provide any of the activities that a server in a server-centric system typically does such as e-mail, authentication or file management.

NAS allows more hard disk storage space to be added to a network that already utilizes servers without shutting them down for maintenance and upgrades. With a NAS device, storage is not an integral part of the server. Instead, in this storage-centric design, the server still handles all of the processing of data but a NAS device delivers the data to the user. A NAS device does not need to be located within the server but can exist anywhere in a LAN and can be made up of multiple networked NAS devices.

NAS provides both storage and file system. This is often contrasted with SAN (Storage Area Network), which provides only block-based storage and leaves file system concerns on the "client" side. Most of the widely used SAN protocols are SCSI, Fibre Channel, iSCSI, ATA over Ethernet (AoE), or HyperSCSI.

Determine the need for NAS: Before choosing a storage platform, consider the applications that will be using the storage -- storage should accommodate the applications, not vice versa. Some file-based application data, such as images and Word documents, are well suited with NAS platforms. Block-based applications, like databases, may achieve better performance through SAN storage. It is also possible to mix architectures using a NAS gateway to allow file-based access to SAN storage.

NAS may be easy to implement and expand, but it can become difficult to manage as deployments proliferate. Before making a NAS investment, consider the changing patterns of storage allocation and use in your enterprise. For example, several terabytes (TB) of NAS might meet immediate needs, but adding several TB per year across numerous NAS devices might soon become impossible to administer. In those situations, an investment in SAN might be more appealing or opt for a large-capacity NAS up front to consolidate storage systems early on. Also, explore potential upgrade paths to learn how future updates will impact storage performance and total cost. For example, more expensive NAS platforms may be more cost-effective over time if they are easier and cheaper to upgrade.

Generally speaking, there are three ways to implement NAS -- use a dedicated NAS system (appliance) with its own local storage; use a NAS head or gateway to access external storage on an array or SAN; or some combination of both approaches. Dedicated NAS appliances are often preferred when simplicity and ease of deployment is most important and little scalability is needed. NAS gateways provide access to considerably more potential storage, but can be more complex to manage due to the provisioning and security implications of SAN storage.

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