A Storage Area Network (SAN) can satisfy hefty storage requirements for large enterprises. For a large enterprise to invest in a million-dollar SAN installation with hundreds of terabytes of storage isn't unusual; however, such power and scalability come with a price. For example, IT staff who are accustomed to managing a Windows 2000 Server environment will need to master new storage management tools, including new Fibre Channel switch infrastructure and different backup schemes. In addition, whereas SANs store data in block format to enhance application server storage performance, file servers use a file-based system to store data, which is incompatible with block format storage. Therefore, you can't use your million-dollar SAN to consolidate your file servers.

In response to these problems, storage manufacturers developed the Network Attached Storage (NAS) head—a protocol handler gateway to an existing SAN. Having no drives of its own, a NAS head uses the SAN for its disk storage. If you use a Windows Powered NAS head, your SAN appears as a standard Windows-based server, and all Microsoft and third-party storage management tools, virus checkers, and group policies work as if they were attached to a standard Windows-based server. This compatibility includes Active Directory (AD) support and the ability to use IP Security (IPSec) support to encrypt data as it travels across the wire.

A NAS head lets you leverage your SAN investment for file-server consolidation. For example, if you have 21 file servers that you want to consolidate, you can move all your files onto the SAN and put three Windows Powered NAS heads in front of the SAN. Each NAS head provides failover and load-balancing capability and handles all the protocol handling necessary to move data from file to block format and back again. Your end users access data and applications as if on a Windows server. And because the SAN stores your data, you can use all the high-end management tools available on your SAN.

A word of caution: Only Windows Powered NAS heads provide Windows server functionality. Non-Windows NAS heads provide some of the same functionality but don't emulate a pure Windows server environment. For example, an IT technician couldn't count on running typical Windows server management utilities with a non-Windows NAS head.

Though NAS heads have only been around for a year, they already represent 10 to 12 percent of the overall NAS market. In fact, some analysts predict that more than half of new SAN installations will include a NAS head because of the increased functionality NAS heads provide. So when you think about investing in SAN, you might also consider a NAS head so that you can get the most out of your SAN investment and your existing Windows-trained staff and functionality.