Network Appliances

Deconstructing the server

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

  • 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.

Win2K with the SAK. Win2K with the SAK provides the tools vendors need to create Win2K-powered server appliances. OEMs can use the SAK with Win2K Server and Win2K Advanced Server, so appliances can scale to up to 8-way Intel Profusion boxes. OEMs install the entire Win2K footprint, then use the SAK to choose which features and functionality to activate for their specific device. This selectivity optimizes reliability and performance in the device's area of functionality. Thus, Win2K on a Web or NAS appliance functions like an embedded OS but, strictly speaking, isn't an embedded OS because it has the full OS footprint. The SAK includes

  • a local console or UI appropriate for monitor display.
  • a browser-based framework for headless management of the server.
  • a Device Driver Kit (DDK) with Microsoft certification of developed device drivers.
  • a software development kit (SDK) that uses Microsoft languages. The SDK provides scripts that help OEMs build Web server and NAS appliances. Microsoft intends to provide scripts for other types of appliances in the future.
  • a reliability framework that includes BIOS failover, automatic mirroring, watchdog timers, and an appliance-monitoring service.
  • build documentation.
  • exposed APIs for adding services.

The SAK interface, which is similar to Microsoft Small Business Server's (SBS's), is task oriented, with each button leading to a wizard. Figure 1 shows the interface page you use to work with network properties. This page was captured on a MaxAttach NAS 4100. The SAK interface is extensible (just as SBS's is); when a vendor adds functionality through a plugin such as an antivirus package or another add-on, that functionality can appear as either a new page in the interface or additional buttons and wizard steps.

Appliances that OEMs create with the SAK can take advantage of all the abilities inherent in Win2K, particularly enhanced reliability in the form of watchdog timers and failovers to redundant devices and services. Win2K appliances support Lightweight Directory Access Protocol (LDAP), the Kerberos security protocol, NFS (for UNIX and Linux clients) and Common Internet File System (CIFS), Novell NetWare and Apple Computer's AppleTalk, and Services for UNIX (SFU) and other network file-sharing services. Also, Win2K supports Fibre Channel, SCSI, and Ethernet, so Win2K NAS appliances that enable support for all three transport protocols can participate in networked storage regardless of the networking implementation you've chosen.

Microsoft is licensing key software products from other vendors to enhance the appliance offerings of its partners with a set of plugins. W. Quinn Associates has agreed to license its StorageCentral SRM software for inclusion in the SAK. StorageCentral SRM provides realtime quota monitoring and enforcement and "best practices" storage-utilization reporting, and it prevents unwanted file types such as MP3 files from being written to an appliance. Microsoft has also announced that it will add to the SAK Columbia Data Products' Persistent Storage Manager high-availability data-protection software for NAS appliances.

OEMs typically use SAK scripts to remove Active Directory (AD) management services from both Web server and NAS appliances because those appliances are special-purpose devices and thus won't be used as domain controllers (DCs—we might see DC appliances one day, but no vendors currently offer them). However, Win2K registers appliances in your domain's AD as servers because that's essentially what they are.

The SAK greatly reduces the number of steps a vendor must complete to create a Web or NAS appliance. The steps are

  1. Specify hardware design, peripheral devices, and associated device drivers.
  2. Install Win2K.
  3. Install the SAK and run the script that chooses the desired components.
  4. Add any OEM features.
  5. Test the appliance.
  6. Run Saprep to remove the keyboard, mouse, and monitor drivers, and install the Null VGA driver.
  7. Run Sysprep to add a unique SID to the appliance when it boots up.
  8. Add a cloned disk to each appliance.

OEMs can get Win2K with the SAK at no cost by sending a request to [email protected] or through Microsoft's standard distribution channels. When an OEM is ready to release a server appliance, the company must obtain a redistribution license from Microsoft.

Talisker and Windows XP Embedded. At the time of this writing, Microsoft is about to add a couple of new members to the embedded Windows family. Technology previews are available for Talisker (the next version of Windows CE) and Windows XP Embedded. XP Embedded follows the model of NT Embedded rather than Win2K with the SAK in that you install only what you need. XP Embedded has the following features:

  • Windows XP's 32-bit code base and protected memory model
  • better performance with accelerated boot and logon
  • improved local and network security with Kerberos and IP Security (IPSec)
  • support for multimedia and browsing with Microsoft Internet Explorer (IE) 6.0, Windows Media Player (WMP) 8, and the DirectX 8 API
  • headless support and flexible boot and storage options
  • support for IP version 6 (IPv6), the Infrared Data Association (IrDA) protocol and ports, 802.11b, and Universal Plug and Play (UPnP)
  • new tools—including Target Designer, Target Analyzer, Component Designer, and Component Database Manager—that provide a more rapid and complete end-to-end development solution

All embedded Windows versions offer a 32-bit OS that can run programs written with Microsoft's visual languages. For more information about embedded Windows, go to

Windows Appliance Types
You can probably imagine many types of Windows server appliances. However, Microsoft and OEMs are focusing their efforts on a few types.

Web server appliances for the ISP market. Microsoft offers a script for building a Web server appliance in the current SAK, and several Win2K Web appliances have already come to market. According to Microsoft, Windows Web server appliances have the following advantages over lower-cost Linux implementations: native support for Active Server Pages (ASP), Microsoft FrontPage, AD, and the Windows Media file format; better performance because of SMP scaling; 128-bit encryption security; and centralized management through Windows Management Instrumentation (WMI) and Microsoft Management Console (MMC).

The SAK Web server script disables the DHCP server, DNS, WINS, RRAS, and DC functions. The script also disables Win2K Server Terminal Services in Application mode (Administration mode remains in use for remote management), Microsoft Cluster service (except for Network Load Balancing—NLB), Authentication Services (authentication requests are passed through Windows Web server appliances to appropriate DCs), and general file and print services.

NAS appliances. The current SAK includes a script for building a NAS appliance for network support of stored Web data and heterogeneous file access for Windows and UNIX systems. Several vendors have released NAS appliances. According to Microsoft, a Windows NAS appliance has the following advantages over its competitors: good scalability, thanks to SMP support; high reliability because of driver signing, system file protection, and other Win2K reliability features; the ability to add the NAS appliance to the network and make configuration changes without needing to power down the appliance; superior performance for the price when serving files to CIFS and NFS clients (as demonstrated in SPECmark tests); centralized management through WMI and MMC; and support for Win2K features such as AD, Dfs, Encrypting File System (EFS), and user and group policy integration. For descriptions of some Windows Web and NAS appliances available from major vendors, see the sidebar "Win2K Server Appliances," page 36.

SBS appliances. SBS appliances provide capabilities such as access to files, printers, a common Internet connection, and other services that small offices require. No major vendors currently offer an SBS appliance.

Networked backup and recovery appliances. Some analysts estimate that as many as 15 percent of all servers deployed in networks have backup and recovery as their primary function. Microsoft sees a market for backup and recovery appliances in the small-business and workgroup (departmental) segments.

Vendors are planning other devices such as document and collaboration servers, messaging servers, and firewalls. You can expect to see these appliances in the next year or so.

A Good Buy
In releasing and promoting embedded versions of Windows for network appliances, Microsoft has taken a big step toward the new model of distributed network services. Although some might see embedded Windows as a reactive strategy, Microsoft is aggressively pursuing both ease-of-use and value-added features. The company's licensing policy is sensible, and the Windows appliances currently on the market are competitively priced with appliances based on other OSs. Several of the first devices seem to have good performance numbers. If you have a Windows shop, you might want to look at some of the products being offered. These products come with good feature sets and offer the best compatibility with Windows—and AD—you're likely to get. The release of XP Embedded brings Microsoft back to the component model in NT Embedded, which could result in a smaller OS footprint in future devices.

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