Network Appliances

Many vendors now offer network appliances, or server appliances, that are dedicated to performing Web services, file services, or other specific tasks. Many appliances use BSD UNIX or Linux as their core OS, but vendors are increasingly offering appliances based on various Windows versions. Microsoft is encouraging this trend by providing tools that help vendors use only the Windows components they need in a server appliance. This new generation of devices represents an alternative to servers—an alternative that you should consider when building your network infrastructure.

The Rise of Server Appliances
Early in the development of the Internet, Sun Microsystems and other UNIX vendors participated in a significant market, selling general-purpose servers as routers. That business largely disappeared when a startup company named Cisco Systems reduced routers to appliances. Mark Santora, Network Appliance's senior vice president of marketing, calls the Cisco model "deconstructing the server," and Network Appliance has applied the approach to file services, delivering a Network Attached Storage (NAS) appliances line that's currently a market leader. Not surprisingly, several of Cisco's top managers are board members of Network Appliance.

Routing is an important but small part of the server business, but vendors can reduce any network service or application server to an appliance. For example, the Oracle9i Application Server offers an enterprise-class database implementation. More common are Web serving, Web caching, and Storage Area Network (SAN) appliances based on a small BSD UNIX kernel or Linux. Table 1, page 34, lists some of these servers.

Most server vendors offer dedicated server-appliance implementations of one sort or another. An appliance approach offers the following benefits:

• Ease of use—Appliances plug into a network and require only minimal configuration. For example, a file-server appliance (aka a filer) might grab an IP address from a DHCP server and require an administrator to enter only security information such as users and groups.



• Good performance—Vendors tune server appliances to perform a particular function and often turn off or remove additional unnecessary system services to create a smaller footprint. Often, appliances are easier to scale than general-purpose servers because they have fewer system components to tune. Recent eTesting Labs NetBench 7.0.1 tests of Maxtor's MaxAttach NAS 4100 (a NAS appliance built using Windows 2000 with the Server Appliance Kit—SAK) peg throughput at more than 46Mbps. (For more information about this performance test, go to http://etestinglabs.com/main/reports/maxtor9_01.pdf.)



• Reliability—Because appliances have a well-established set of operational parameters and run fewer unnecessary services, they can often be more reliable than general-purpose servers. Like general-purpose servers, appliances offer fault-tolerant features such as redundant internal components, load balancing, and clustering.



• Remote management—Appliances are headless (i.e., they don't need a monitor). Instead, they have special management software, either a console or Java-based component, that lets you manage them remotely over a network or the Internet. The management software for general-purpose servers isn't always enabled for remote administration.



• Lower cost—Because appliances reduce the functionality of a general-purpose server to a single function or set of functions, they're often cheaper than general-purpose servers of similar power.

Of course, there are some trade-offs when you purchase an appliance. The arguments against appliances include the following:

• Limited functionality—Vendors design an appliance to serve one particular need. Should your company's needs change, you can't modify the appliance to suit another purpose.
• Faster obsolescence—As technology changes, an appliance might not be as adaptable as a general-purpose server, so its useful lifetime might be shorter.
• Limited software and management options—An appliance ships with a limited set of software and configuration choices.

You can modify and upgrade some appliances, such as Compaq's TaskSmart N2400. However, for closed appliances such as the MaxAttach NAS 4100, all these arguments apply.

Embedded Windows and Appliances
The server-appliance segment is a tiny fraction of the embedded-systems marketplace but a highly profitable and growing one. Microsoft offers embedded versions of Windows CE and Windows NT and a kit for modifying Win2K to create appliances. Device manufacturers use each OS for a different purpose.

Windows CE 3.0. Windows CE 3.0 is a modular, realtime OS for small and mobile devices, including the popular Compaq iPAQ and the Hewlett-Packard (HP) Jornada Pocket PC. (A realtime OS constantly monitors conditions and acts on its own, in contrast with regular Windows, which is an event-driven, reactive OS.) Windows CE offers rich communication services, the ability to create a small and highly customizable memory footprint, and support for a wide range of processor types and families. Vendors can choose from more than 200 Windows CE modules, including TCP stacks, keyboard I/O, and modem support, and only a few of the kernel services are required components.

NT Embedded 4.0. NT Embedded 4.0 contains the entire NT 4.0 OS and its services to build feature-rich embedded systems, but OEMs don't necessarily install the entire OS footprint. Microsoft describes NT Embedded as "a componentized version of the Windows NT 4.0 operating system," meaning that OEMs can choose which pieces of the OS to install.

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