Both NAS and SANs will play prominently in this networked storage arena for years to come. For the buyer of this technology, it is important to evaluate exactly what the needs of the network and users are, not only now, but in the future. From there, the answer should be obvious. For a company with long-term growth likely, a combination of the two approaches will likely prove a winning strategy. In fact, SANs and NAS can be used together.
People think they compete, but they're actually quite complementary.
For example, a NAS appliance can be attached to a SAN if one is implemented down the road. In addition, NAS vendors are adding SAN-like management capabilities to their products. Basically, it boils down to this. NAS is more of a component, or an appliance, that can be added to an existing network, while a SAN is more of a separate network architecture consisting of a variety of storage devices and switches. SANs are much more scalable and flexible, and they provide direct disk access, which is a requirement for some applications.