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If you've decided to purchase a NAS device, next consider task, storage size and network capability. There's no one-size-fits-all solution for NAS devices, regardless of what the vendors might say.

The NAS market can be broken into three segments: the low end, which includes devices from Maxtor Corp. and Quantum Corp.; the midrange, including appliances from Land-5 Corp., Network Storage Solutions (NSS) and Procom Technology; and the high-end market, which comprises devices from Compaq Computer Corp., EMC Corp., IBM, Network Appliance and other vendors. However, these boundaries between the groups are becoming muddled.

If you define the market by total storage, some of the low-end devices get bumped into the midrange and some midrange appliances become high-end devices. If you define the market by features, the same shifting may occur. Features grow richer while density goes through the roof. At one time, features like a SCSI port for local tape backups and multiple network interfaces were found only on midrange and high-end devices, but now you can find such features on some low-end devices, too.

We'll see price crunches, feature packing and consolidation in the NAS market, and that's all good for the end user. Unfortunately, though, it's likely that some of the smaller, less-established vendors will not survive.

Among the first questions to ask is, What are you trying to store? If your network people are moving limited data from location to location, a small NAS device is suited for quick and safe data backups--and it fits in your briefcase. Are you looking to set up storage for a specific group--an engineering team using CAD, a digital photography team or a team with large storage needs? Maybe you need to put your users' home directories on new storage. In these cases NAS devices can provide flexibility and save you money.

For the engineering team, you'll want a small, portable storage device. The device need not have extended backup capabilities, such as NDMP (Network Data Management Protocol) or RAID, or any other type of advance data safeguards. It should be large enough to do the job, hook easily into your network--or directly to a PC via Ethernet or USB--and get the job done.

With the astounding capacity of today's simple IDE devices, these little units should be not only inexpensive, but more than enough to do simple data-transfer jobs or handle data support for a single voracious user in need of some extra data space. This defines the bottom of the low end of the market.

Moving up the food chain (but still in the low end of the market), there are low-cost devices that serve more of a permanent-placement roll. These devices offer RAID capabilities, NDMP support and sometimes even multiple NIC interfaces. Earlier this year, we tested two appliances in this category--the Maxtor MaxAttach 4100 (see "Maxtor MaxAttach 4100: Windows-Powered Storage," May 14, 2001) and the Quantum Snap 4100 (see "Snap Server 4100: A Storage Solution That's, Well, a Snap," April 16, 2001). When we asked Quantum and Maxtor officials why both products have the same model number, they responded in typical vendor fashion: Each said the other copied the name.

Regardless of model-number madness, some devices in this category offer features previously found only on midrange NAS devices. For instance, Maxtor's 4100 has an external SCSI port for backup to local tape. These rack-mountable devices offer up to 320 GB of storage and consume only 1U of precious rack space.

Some units even offer a gigabit copper interface for increased network throughput. Often priced below $5,000, these devices can solve some of your departmental-level storage problems in a hurry.

Next, the midrange market consists of machines that often can be expanded to house more than 2 TB of data, and have SCSI drives and a multitude of elements designed for the enterprise user (see "Midrange NAS: Happy Medium," October 2, 2000). Usually larger than their low-end cousins, these boxes can handle more connections at a faster rate. They also tend to run on bigger hardware.

Most small NAS devices are Intel Pentium or Pentium II systems, while the midrange devices generally run fat Pentium IIIs in excess of 800 MHz with 256 MB or more memory. This, along with the greater effort going into the engine, gives midrange systems a noticeable performance boost (see Sidebar, "Fission or Fusion?"). This system class also offers redundant network connections for load-balancing and failover, and many integrate with backup software from Legato Systems, Veritas and others.

Another feature in some of these midrange machines is the snapshot, which will take a picture of your data on the NAS device at any given time and let you quickly restore it to its original state. This is especially useful for database work. Having a problem with the database update and need to put the old version back fast? Voila! There it is. This is a very useful feature for production systems with a limited window for downtime. Some units in this bracket have adjustable cache schemes that provide the ability to customize the cache for maximum performance in your given application.

At the high end we find monster NAS devices that range from being little more than the midrange devices with more capacity to multiple refrigerator-size prepackaged Fibre Channel SANs with NAS heads on them. Typically, these units have the ultimate in throughput, network flexibility and integration into your management infrastructures (including Computer Associates International's CA Unicenter and Tivoli's TME). Getting into this kind of system is a big deal as you're making a commitment to use the device for a large production system or, in the case of a smaller shop, all your data storage. Traditionally, this is the area where the comparisons with full-blown SAN networks are made, but you should stay focused on your specific needs.