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.
Even NAS gateways have capacity limits. Even though a NAS gateway is intended to use external storage resources, there is still a finite limit that the gateway can address. For example, Hitachi NAS Blades can be clustered to support up to 512 terabytes (TB) per cluster. This isn't a problem for most organizations today, but potential storage limits should always be considered when planning a new gateway deployment.
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. For example, an NS700 series NAS gateway from EMC does not provide RAID or disk scrubbing, but the gateway supports Symmetrix and Clariion storage, which does include RAID and disk-scrubbing features. Changing storage platforms may add new features or remove existing features, and this can easily change the way that data is managed through the gateway. Storage administrators must consider how changes to the storage infrastructure will influence NAS capabilities.
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 EMC Corp.; EMC Corp.; Celerra NS40G/NS80G NAS gateway