Network attached storage (NAS) appliances typically contain their own internal storage resources. Storage capacity is expanded by simply adding more disks to the appliance. Obviously, this only allows users to scale up to the capacity limit of the appliance. NAS gateways overcome these inherent limitations of scale and flexibility by utilizing externally connected storage. In some cases, the external storage may be a standalone disk array. It's also common for a NAS gateway to share storage through a storage area network (SAN), allowing users to consolidate their NAS data on SAN storage and realize the benefits of high performance and redundancy. Major NAS vendors offer tools that can migrate data from NAS appliances to their NAS gateway products, which can also support all NAS protocols and many operating systems environments.
Evaluate interoperability between the gateway and storage. Not all gateways work with every storage subsystem. This is particularly important if you're connecting to SAN storage. For example, the Bobcat Series NAS gateway from ONStor Inc. supports disk arrays from disk array vendors, including Hitachi Data Systems Inc. (HDS), EMC, IBM and HP. It's important to start by checking the vendor's compatibility matrix, but in-house testing is also strongly encouraged to verify compatibility.
Remember that some features move to the storage. By moving storage outside of the NAS gateway, remember that some features will be dependent on the storage subsystem(s) being used.
Consider the connectivity. With external storage, connectivity is essential to ensure adequate performance across the user base. In most cases, you can expect an array of Ethernet and Fibre Channel (FC) ports.
Evaluate standard features. Pay close attention to the variety of features that ship standard with the NAS gateway, including clustering, mirroring, replication, reporting, volume management and so on.
Evaluate optional features and licenses. Don't just assume that every function and protocol is supported as a standard feature. There are often many features available as options that can inflate both the initial and ongoing costs of a NAS gateway.
Consider the impact of virtualization. Virtual server capability allows NAS gateways to appear on the LAN as a complete NAS device with a unique identity, IP address and security authentication. This allows NAS gateways to be relocated, maintained and scaled without disruptions and data migrations. Storage virtualization allows capacity to be added and configured as necessary, while eliminating wasted (unused) storage space.
Read the rest of Stephen J. Bigelow's article at SearchStorage.com.