• United States
by Tom Joyce, special to Network World

NAS gateways allow IP access to SANs

Apr 12, 20043 mins

A NAS gateway bridges the NAS and SAN worlds by connecting IP networks to Fibre-Channel-based storage. These highly optimized file servers help corporations preserve their storage investments.

Network-attached storage  quickly has been adopted in corporations because IT managers were drawn to NAS appliances’ low cost and quick and easy deployment. But the flexibility comes at a price – the more islands of storage that surface, the more they complicate the task of storage management. As a result, many companies have rolled out storage-area networks to consolidate their storage environments.

A NAS gateway bridges the NAS and SAN worlds by connecting IP networks to Fibre-Channel -based storage. These highly optimized file servers help corporations preserve their storage investments.

A shift in storage

NAS gateways not only offer a cost-effective means of consolidation but also lower the cost of adding new NAS applications to a SAN infrastructure.

Implementing a NAS gateway to access SAN storage increases flexibility and scalability, and delivers greater performance by letting administrators mix different classes of storage arrays and multiple tiers of storage, such as Fibre Channel and Advanced Technology Attachment. Unlike a traditional appliance, a gateway is not limited by the storage included within an appliance and can access resources from multiple, high-performance storage arrays on a SAN.

A NAS gateway gives IP-connected clients file-oriented access to block-level storage on a SAN and processes requests from clients via standard file-sharing protocols, such as Network File System and Common Information File System .

When a gateway receives a client request, it translates the request and sends a request for block data to a storage array. The array processes the request and sends it back to the gateway. The gateway then translates the block information to file data and sends it to the client. This process is seamless and transparent to end users.

One distinction between NAS appliances and gateways is how they attach to the storage. NAS appliances connect directly to the storage housed within the appliance.

The NAS gateway, which connects to an IP network, is attached to a Fibre Channel switch that in turn connects to Fibre Channel storage arrays. Using this methodology, the gateway can access storage resources from multiple storage arrays connected in the SAN.

The physical connection from the gateway to the SAN is via 1G or 2G bit/sec Fibre Channel host bus adapters in the gateway. The host bus adapter uses optical cabling to connect to the Fibre Channel switch on the SAN, which also is connected to the storage subsystem.

Once the gateway is physically connected to the SAN, administrators must configure appropriate zoning from the storage array(s) to the gateway. In most cases, storage ports can be shared between the NAS gateway and other application servers on the SAN.

By supporting a variety of SAN connectivity devices, mixing and matching multiple tiers of storage, and using existing management tools for SAN data, NAS gateways optimize and extend the useful life of storage assets. As a result, companies can lower administrative costs, avoid unnecessary hardware purchases and increase utilization of high-end features of a SAN-connected storage array.

Joyce is senior director of NAS marketing at EMC. He can be reached at