By SEAN FULTON
Few debates in networking circles excite as much passion as the near religious zealotry surrounding the choice of an operating system. This seems a little strange since most professionals agree that an OS choice depends on one criterion only: suitability to the task at hand. You pick the best tool for the job. It's that simple.
As recent as two years ago, network operating systems engendered holy war debates with every product release. But with the advent of intranets, server operating systems just don't seem to get the big headlines anymore, and that's a mistake. Your server operating system can have a profound impact not only on intranet server performance, but also on what kinds of intranet applications you'll be able to run.
Important factors to consider in picking an operating system are hardware support-both current and future purchases-legacy application support and the ability of the development staff to build suitable applications. Additional considerations might include a support staff able to maintain the target platform and, of course, cost.
Performance is an important factor in selecting an operating system, but it is one that depends largely on your particular Web application and your choice of hardware-so much so that comparing it in the abstract doesn't make much sense.
To help sort out some of the complex decisions that go into choosing a Web server platform, we asked the makers of six popular operating systems used on corporate Web server systems to provide us with products and information about their systems so we could compare them on an Intel platform. We received the latest versions of SCO's Enterprise Server, Microsoft's Windows NT, Red Hat Software's version of Linux, Berkeley Software Design Inc.'s BSD/OS 3.0 and Walnut Creek's distribution of FreeBSD 2.2.2 for testing. Sun Microsystems was unable to provide a copy of Solaris 2.6 in time for our testing.
We examined the systems using several criteria, including the robustness of the system; its stability-as best as could be assessed from several days working with each product; the completeness of its feature set; and the types of software that could be added to it easily and at what cost.
We chose a specific hardware platform and tested the five operating systems using four sample Web sites downloaded from the Internet. Our point was not to show each operating system in its best light, or to try to predict how well these different systems would work in an environment where experts have carefully tuned each OS to its peak performance. Our goal was to develop a benchmark for comparing relative, out-of-the-box performance in a basic Web server scenario. The tests show how the different systems stack up against one another, but remember that your mileage may vary.
So how did the different systems perform? As expected, the Unix systems were generally faster and more complicated to administer than the NT machine. But this is not about Unix vs. NT, it's about Web server platforms.
FreeBSD had the best performance in the short run, pulling to an early lead with 100 users, then falling back, we believe, because of some resource bottleneck, but the OS did not produce an error condition to alert us. BSD built on FreeBSD's early lead and seemed to be more finely tuned out of the box for high-volume Web serving. Linux, the perennial favorite among the do-it-yourself crowd, pushed more data and scaled more effectively with one and two CPUs than NT, which must give a great sense of satisfaction to the Linux development team.
And though it will stick in the throats of many Unix systems administrators reading this, we must also point out that Windows NT performed quite well. The system scaled gracefully as the user load increased, and even though it was beaten at most data points by at least one Unix competitor, the myth that NT does not have the horsepower to run a high-performance Web server is untrue. Having gotten that out of the way, let's talk about some of the less controversial surprises.
The free operating systems we looked at, Linux and FreeBSD, are worthy of consideration for mission-critical Web serving. They perform well, have robust feature sets and are supported by a number of public domain Internet packages, which makes them fairly simple plug-and-play solutions in many environments. While you won't find features geared toward a high-priced corporate environment, such as the ability to run Windows applications or to have compatibility with Novell Directory Service on these systems, they still do a good job as a nuts-and-bolts Web server.
As for support, anyone who has ever waited more than an hour for technical support knows that unless you're a large company with enough clout or dollars to get those special support contracts, your fastest solution to a problem is a Usenet newsgroup or peers using the same product. The benefit of a free OS is that you have source code available to fix the problem once you identify it. That's not a technically lightweight proposition, but for those with the mental brawn, it can save hours of frustration.
Microsoft, SCO and BSDI, on the other hand, do have the ability to develop strategic relationships with hardware and software vendors. That gives them better access to the tools needed to write a device driver or port an application. It also gives them greater support among applications developers and compatibility with more hardware systems than you'll find from any free OS.
Microsoft is probably the most advanced at this, while SCO has great hardware support and a dazzling array of subsystem and middleware vendors that either distribute or support its products. BSDI also is moving in this direction, but because it still is a much smaller company, it hasn't covered nearly as much ground as its competitors.
So, when all factors are considered, which operating system is right for your mission-critical Web server? It depends on your needs and the experience of your team.
If Unix knowledge isn't a problem and your needs go beyond the features provided by standard Web servers, then FreeBSD or Linux are ideal. They offer high performance and access to source code, which gives you the ability to fix your own problems and add your own features. If your technical staff is Unix-literate but not able to make its own OS fixes, then BSDI is a good choice. For integrating the Web server with your other data systems, SCO can't be beat, and if your needs require straightforward, no-nonsense installation and setup, Windows NT makes sense.
BSD 3.0 is a robust, full-featured operating system that is being carefully crafted by its developers into what might become the ultimate Internet service provider platform. Its performance in our benchmark tests was stellar, scaling gracefully under load and handling more connections per second than any other operating system we tested.
The system comes with every major software package required to set up and maintain an Internet presence on a single, high-performance machine, including the Apache Web server, a Kerberos server for user authentication, a RADIUS server for authenticating users dialing in to terminal or access servers, BIND for Domain Name Service, sendmail for mail transport, and POP3/IMAP support for local E-mail readers, and Point-to-Point Protocol for providing dial-in service using a multiport board. Any Webmaster or service provider with a working knowledge of Unix will find this an ideal operating environment.
The OS combines the straightforward elegance of FreeBSD with some of the configurability of Linux or SCO. The BSD development team has worked hard to make common ISP tasks like setting up a dial-in modem pool or configuring authentication schemes as simple as modifying a few text files, and yet configuring the kernel or other major system component retains the sort of direct, programmer-like control found in FreeBSD.
As with the other systems we looked at, there is a graphical configuration utility that novice administrators can use to set up and tune the system, but that isn't the real surprise with BSD.
Unlike the other operating systems, which supply a series of components from which an administrator can build a Web server or, say, a dial-in modem server, BSD's development team has clearly identified the tasks and subsystems required of an Internet server and preconfigured those systems for use. It's as if the OS has already been almost completely set up as an Internet server save for the particular IP addresses or brands of modems being used.
For example, the process of hosting multiple domains is well documented in the system manual and, where possible, much of the configuration has already been accomplished. Adding IP addresses to a file on the filesystem will cause the network startup scripts to automatically bind the additional IP addresses to the system's network card, and the sendmail configuration file (a monster for even the most experienced navigator to administer) has already been set up to support virtual domains. All the administrator needs to do is add the domain names and local addresses to a mapping table.
BSD also supports a surprising array of new, high-performance hardware like 100Base-TX network cards, Ultra/Wide SCSI controllers and high-speed multiport boards, thanks to the company's aggressive pursuit of relationships with manufacturers of hardware and peripherals. These manufacturers tend to follow users and applications, so BSD is no doubt aided in this effort by its ability to run off-the-shelf programs written for FreeBSD, Linux or SCO. Driver updates are released several times annually, but only to users who have paid to maintain a support subscription. This is unlike SCO, which offers most patches and fixes to customers over the Internet at no charge.
In our performance tests, BSD scaled elegantly under load from 205 connections per second under a 100-user load to 326 connections per second under a load of 300 virtual users. Its throughput also jumped from 630 kilobytes per second at 100 users to 827 kilobytes per second with 300 users.
The issue of licensing is one factor that may slow BSD's still- rapid growth. In terms of performance, it did only slightly better than FreeBSD, but a little worse than Linux, both of which are available at no charge. Although the company caters to Webmasters and ISPs, its products do not come with source code and have a per-user licensing structure that may blunt its popularity on the Internet. The software is priced at $995 for a 16-user copy, up to $2,995 for an unlimited-user copy.
The company also lacks the marketing muscle of SCO or Microsoft, making it a difficult sell in corporate environments where strategic relationships with hardware and software developers are as important as the OS's fundamental code.
BSDI must continue to provide significant value-added improvements to the core OS to build critical mass among hardware and software development partners. The company must continue its pursuit of support among peripherals makers and applications developers so it can justify its licensing fees by offering products and ports that the FreeBSD or Linux community can't match.
To augment its already impressive performance, BSDI is planning to add multiprocessing in an upcoming release, which should win the company greater support from corporate customers who want to use it as a platform for high-volume Web serving.
Although the product delivers great performance as a Web server and networked workstation, its cost may drive some customers away. But with speed like this and active support from hardware and applications vendors, BSD will find many welcome homes among the Web servers of the Internet.
FreeBSD is a simple, elegant Web- hosting platform that takes everything the University of California at Berkeley ever did for Unix and networking and packages it into a clean, straightforward platform.
In our tests, the system leaped past its competitors with 100 simulated users, but then seemed to peak and fall back with 200 and 300 users. Performance went from 232 connections per second and 598 kilobytes per second of throughput at 200 users to 188 connections per second and 606 kilobytes per second of throughput. The system could definitely benefit from some careful tuning to accommodate the additional workload.
FreeBSD includes all the software needed to set up a fully functioning Web server or networked workstation. All distributions come with complete source code, and a handful of Web servers, Web management tools, Perl converters, shells and CGI programs designed to make it a top-drawer Web server right out of the box.
Also included are the latest versions of BIND for DNS, sendmail for mail distribution, a PPP package for remote dial-in, and optional Kerberos authentication for local and remote user authentication. What makes this package especially nice is that like the BSD system, Kerberos is integrated into the core operating system for authentication use by all utilities, eliminating the chance that someone will crack an improperly protected password file.
FreeBSD is used by a number of high-traffic Web sites, including Yahoo, which maintains a server farm of more than 50 FreeBSD machines, and Walnut Creek CD-ROM, which serves up 106 gigabytes of data to more than 2,000 users from its FTP site daily.
This OS clearly lacks the "let's cover everything" approach of Linux, but because of its tightly controlled development environment-fewer than 15 people are listed as core contributors-the things this operating system does, it does extremely well. That comes as no surprise since BSD is one of the last true remnants of the original Unix development effort at Berkeley.
It should be noted that there are other free versions of BSD available on the Internet, including NetBSD, which runs on a variety of different CPU architectures, and Open BSD, which is used chiefly in the academic and research communities. FreeBSD is written exclusively for Intel platforms and seems to have the largest following among ISPs and Web-hosting companies. BSDI's product, BSD/OS, which also hails from the original Berkeley effort, is remarkably similar to this operating system but with some polish added to justify the price tag.
Clearly, FreeBSD is not for the faint of heart. It lacks the mass of configuration files and package management utilities of Linux, and it doesn't have the sophisticated systems management tools that SCO has spent years developing. While anyone with a Unix background can install and configure a FreeBSD system in minutes, tuning it to augment performance or enhance its core feature set requires at least minimal programming experience.
For example, Linux has a long but fairly straightforward configuration file for adding device support to the kernel, but no tools to optimize kernel performance and very little documentation on how to do so by hand. SCO has about a dozen tools and volumes of documentation for literally every single kernel parameter, which makes up for the lack of source with which to hack out yet another Unix variation.
FreeBSD has a single basic configuration file with C define statements; the file is used to parse the kernel source into a source tree for compilation using the Unix program called "make." No fancy configuration utilities, no neat toys. There is a pleasant mix of device support and performance tuning options in the configuration file, and these options are well documented both on the Internet and in "The Complete FreeBSD" by Greg Lehey (Walnut Creek CD-ROM). FreeBSD supports a wide variety of high-performance networking peripherals and hard disk controllers, making it ideal as a networked workstation, Web server, router or even Usenet news server. Its support for multiport boards is lacking, however, which makes it a rather poor choice as a platform for a dial-in modem server.
Overall, this release is solid and performs well under moderate load. With adequate experience and some tuning, there is no question this system can perform well. Its price tag, history and scalability make it a fine platform for an Internet service provider or a large company planning to set up a scalable yet inexpensive Web server.
Linux was first introduced on Oct. 5, 1991, by Linus Torvalds at the University of Helsinki, Finland. It was a pet project that he said heralded back to the days "when men were men and wrote their own device drivers."
Today, Linux is a remarkably fast and stable POSIX-compliant Unix operating system that runs on a variety of hardware platforms including x86, Sparc, MIPS, Digital Equipment's Alpha and even the Motorola 68000 architecture, and is actively being supported, documented and developed by thousands of hackers, administrators and users all over the world.
In our performance tests, Linux soundly licked all its opponents, including BSD and NT, which cost hundreds of dollars more. What's more, the system scales beautifully, from 153 connections and 646 kilobytes of throughput with 100 users connected, to 230 connections per second and 996 kilobytes of throughput with 300 virtual users connected.
Linux also showed a boost in performance with the addition of a second CPU, although at 300 virtual users it seemed to sputter a bit under the extreme load and fall back to a clip that was below its performance with 100 users.
The software is free under the GNU Public License, and despite the wide variety of software that runs on it, including X-Windows, TCP/IP networking and a slew of compilers and debuggers, Linus himself still controls the "official" kernel releases (although an entire tree of "unofficial" patches is constantly available for those who can't wait for formal approval).
As an operating system, Linux is like an overweight, hairy uncle who just seems to grow on you. Because of its widespread development model, it supports just about everything. Because of the lack of centralized control, it handles some functions better than others, and there are even a few functions it can't do well at all.
No matter what piece of hardware you have, someone somewhere on the Internet has a Linux driver for it. While this may make initial hardware configuration a bit like an Easter egg hunt, Linux is still fun to use, reliable and quite capable as a Web server platform once it's up and running.
The benefit of Linux over FreeBSD is that there is a larger, more diverse development community. Obviously, the benefit Linux has over any of the commercial operating systems examined here is that it is free. There are many different versions of Linux available, some of which aren't exactly free. The three most common are Red Hat, Debian and Slackware. All three share the same kernel and source tree, but each bundles slightly different components and has a slightly different design and implementation policy.
All Linux versions can be downloaded and installed for free over the Internet. Slackware, Red Hat and other companies sell copies of their versions on CD-ROM for anywhere from $10 to $99. The money goes to defray the cost of producing the CD-ROM, and to help recover the investment the companies have made enhancing their particular releases.
Slackware has long been known in the Linux community as the most up-to-date, if not completely polished, version of Linux. Yet another version, Debian Linux, is maintained and updated on the Internet by a tightly knit development group of more than 100 that steers away from commercial distribution. Red Hat, which is the version we used for our test, is being developed and maintained by Red Hat Software of Durham, N.C.
It is important to note that, like Unix, Linux distributions can vary significantly in terms of the revision level of the kernel, libraries and key software components. While the 2.0.30 kernel was the most recent and stable kernel available at the time of this review, not every Linux distribution was up to that level. Fortunately, most distributions can be upgraded easily by retrieving a current kernel source tree off of the Internet and building it on your target machine.
The Red Hat Release 4.2 we examined includes all of the latest Internet/intranet programs such as the Apache Web server, BIND for DNS, the WU FTP server, as well as sendmail as a mail transport, POP/IMAP daemons, PPP, SLIP and a full Usenet news server implementation. This release does support shadow passwords, Network Information Service (NIS) and NIS+, but it does not include a native Kerberos database for user authentication, or RADIUS for remote dial-in authentication.
One feature peculiar to the Red Hat distribution that illustrates the attitude of the Linux development community as a whole is a subsystem called Programmable Authentication Modules, or PAM, for user authentication.
PAM is an attempt to separate the code required to authenticate users from the applications that require authentication. Its creation stems from the development community's frustration at having to constantly recompile applications each time a new user authentication scheme is developed. Originally, Linux and all Unix distributions kept user information, including the encrypted password, in a publicly readable file. Several alternative schemes were developed, such as shadow passwords and Kerberos, but each method required developers to add support for the authentication scheme to programs like login and FTP.
Red Hat's solution, working with developers at Sun and on the Internet, was to develop a set of authentication libraries that were application-independent. The result is that any application that requires user authentication can simply query the PAM library, which then authenticates the user based on the appropriate authentication method, either straight password, shadow password, NIS or Kerberos.
Another feature unique to the Red Hat release is the Red Hat Package Manager, or RPM. This utility works like the old SCO Custom utility or like the Windows 95 uninstall program, allowing users to easily add, remove and update software packages as a complete package rather than as a file at a time. Combine RPM with Red Hat's simple, straightforward install and this version of Linux can easily compete on ease of installation with any commercial Unix.
Once the Linux system is set up, you'll find a conventional, slightly BSD-biased Unix operating system that has many of the features needed for an Internet server. Configuration of most system services can be done either by editing Unix text files or in an X-based interface using Red Hat's own graphical management tools. These tools are well thought out and thorough, and easily give the first-time or novice Unix user a jump-start on systems administration.
Under the hood, you'll find the Linux kernel to be fairly robust, supporting both ELF and a.out binaries, dynamic loading and unloading of kernel modules, and support for a variety of hardware platforms. Linux will run binaries compiled for other operating systems as well, including SCO, DOS and BSD variants.
The Linux community has done an excellent job documenting the workings of the Linux system and the huge number of component software packages available for it. A handful of key Web sites around the world contain thorough and complete how-to documentation maintained either by developers or zealous observers of a particular section of the system.
Although kernel documentation on adding and removing support for different peripherals is fairly complete, documentation on tuning device support or kernel run-time parameters ranges from nonexistent to sparse. In many cases, the only source of information is the C code itself or in how-to documents. This is an area the Linux community would do well to work on, as it would allow users who are not die-hard programmers to optimize and tweak the system to its full potential.
But even without the secret keys to the kernel's performance- tuning variables, Linux leaves other operating systems in the dust in its ability to churn out Web pages. Although it lacks branding as a "true" Unix operating system, Linux is Unix in spirit and in its POSIX compliance. The OS embodies many of the principles and ideals that have evolved through the 25-year evolution of Unix, and it does so in a way that welcomes innovation and inspiration.
Add to this hippie idealism the fact that, for the most part, Linux is a rock-solid system that supports a wide range of hardware and outperforms most other systems, and you have the formula for a formidable server outside or within corporate halls.
Microsoft Windows NT is extremely simple to set up and use, capable of turning even a novice computer user into a full-fledged Webmaster in a matter of minutes.
What's more, it performs comparably with the Unix systems we tested, ending the myth that NT is not capable of acting as a high-volume Web server. For a single CPU, the system scales quite capably under load as a Web server, with very little tuning or optimization required. It does not show any marked improvement, however, with the addition of extra CPUs.
Without the Olympic-size hurdle of having to master the complexities of a multiuser Unix operating system, people with no experience in systems administration or systems management are able to handle a large, complex Web installation with just a few mouse- clicks. This makes it easy for nontechnical users to become systems administrators or Webmasters, which is fine until something goes wrong or security is compromised. At that point, the system needs a more seasoned administrator.
Another potential problem with NT is that it lacks the historical perspective that all Unix operating systems have.
Although Unix implementations vary significantly in their approaches to specific problems or tasks, all Unix implementations-and Linux-share a similar core logic and approach to systems management that has evolved over the more than quarter of a century the system has been under development.
NT, on the other hand, is a relatively new approach to system design and management, one in which the default mode of operation is to hide complex configuration and management decisions from the user or administrator. Unfortunately, it's precisely these types of decisions that can mask potential new security flaws.
As far as performance is concerned, the system started its 10-user runs on par with the Unix systems we examined, then scaled gracefully with one CPU to a peak of 247 connections per second and 694 kilobytes of data transferred under a load of 300 users.
A second CPU didn't do much to enhance NT's performance, though, indicating that the scalability of adding additional CPUs to an NT machine is not as obvious. With two 180 megahertz, Intel Pentium Pro CPUs in our test machine, NT actually managed fewer connections per second (228) and only slightly higher throughput (705 kilobytes per second) than with a single CPU.
Contrary to what most people think, much of an NT system can be tuned or modified using text configuration files-.INI files in the WINNT directory-or through the system Registry Editor, which provides access to most of NT's internal structure. This type of configuration and tuning requires experience and a level of technical expertise, as well as extensive documentation both from application developers and Microsoft.
For basic use, however, anyone who has ever used Windows 95 can set up and manage an NT server system. This makes it ideal for corporate environments that have standardized on Microsoft products, or for workgroups and small businesses with little technical experience.
The base operating system comes with a fully functioning Web, FTP and gopher server, all of which can be easily administered through the point-and-click Windows interface. Additional packages that ship with the product are Microsoft's implementation of DNS, TCP/IP printing, Remote Access Service for setting up a dial-in PPP modem pool, and an SNMP suite for systems management.
Adding a Web site to the NT server is as simple as storing the documents in a directory, telling the server which IP address (or domain name) is to be served by that directory, and then restarting the Web server process. In our tests, NT had some difficulty translating server-size image maps, particularly those that used relative path names that were acceptable on the Unix systems. These problems were quickly remedied, however, by adding the full path name of the files to be retrieved to the map file. Anyone using NT as a platform for their Web service would have built the map files this way from the start.
A mail transport system is not included with the base NT distribution and administrators planning to use a heterogeneous mix of machines on the network are limited to either Novell or Microsoft's network authentication systems. There is no Usenet news server included with the system, nor is there a Telnet daemon. More important, administration of the system requires a console or console redirector, making remote NT systems more difficult to maintain.
Because it's easy to administer and it works seamlessly with Windows 95, Windows for Workgroups and Novell environments, NT has gained tremendous support from hardware and software developers. A growing number of high-performance devices only support NT, leaving SCO, BSDI and the Internet community to develop drivers for other OSs.
A good example is the Dell PowerEdge RAID controller, which has 16 megabytes of cache and produced outstanding performance in the Dell 4100 machine we used to test these operating systems. The only server system we tested that was natively supported by Dell was NT, so we had to take the controller out of the machine and use the embedded Adaptec 7880 SCSI controller on the Dell motherboard for our tests to achieve a level playing field.
Since hardware support is an important criterion in selecting an operating system, companies choosing their next Web server OS should pay attention to current market conditions.
If they are looking at an OS besides NT, they should ask their hardware vendors what sort of support is available.
One final note on NT: Although the Web server that we tested performed flawlessly, there remain some nagging problems with NT, which we have yet to resolve. Our benchmark application ran on five NT servers, all communicating with each other and making requests of the Web server. During the weeks we ran our tests, we encountered problems at least once a day where the NT benchmark machines needed to be rebooted for no other reason than because they had stopped responding either to the benchmark program or to keyboard or mouse input.
While this may very well have been a problem with the application, or with the application's extremely heavy use of NT's networking stack, it's troublesome that the entire machine needs to be rebooted because of an application error. That rarely happens on a Unix system, and many Web servers average four months or more of uptime under heavy load before needing to be rebooted.
Of course, the NT server we tested didn't require rebooting at all, indicating that Microsoft's integration of IIS 3.0 with the base OS is rock-solid.
Enterprise Server 5.0.4 from the Santa Cruz Operation is based on the grandfather of all server operating systems, and although it may not be as spry at some tasks as its younger competition, with age comes wisdom, experience and reliability.
At this system's core is an AT&T-based System V Release 3.2 Unix kernel that has been used, abused and hammered on by systems administrators, developers, integrators and users for years. Rather than chasing down kernel bugs or porting the system to yet another hardware platform, SCO has spent its time adding functionality and integration services to its core product.
While the underlying system and core services are stable, reliable and one of the most thoroughly documented in the industry, SCO has added to this equation layered services that integrate the product tightly with Novell, Windows, Macintosh and mainframe environments. It also has added an array of tools designed to increase system performance, enhance scalability and improve manageability of not just one Unix server, but of server clusters as well.
The company's next release, a 64-bit system code-named Gemini, is said to be based on the System V Release 4 kernel AT&T developed before it sold Unix to Novell. In 1995, SCO acquired Unix and then two years ago, Novell's UnixWare. It has been working to integrate the new kernel with its existing product.
The Web server software that came bundled with the OS, Netscape Communications' FastTrack Web server, is a bit underpowered for the heavy-duty jobs, but suitable for small-to-midsize Web sites. SCO also offers Netscape Enterprise Server, but only as an extra-cost option.
The operating system didn't perform well in our tests, and several conversations with SCO's technical support team failed to clearly identify the problem. It appeared from our assessment that there was a problem with SCO's driver for the Intel EtherExpress Pro 10/100 network card running full-duplex at 100 megabits per second. When the driver was reconfigured to run in 10 Mbps mode, it actually ran faster than at 100 Mbps.
With a single CPU, the SCO-based server peaked at 122 connections per second with 100 running virtual users, but then trailed off to a meager 83 connections per second on a 300-user load. Its throughput suffered the same result, peaking at 413 kilobytes per second at 100 users, then dropping off to 296 kilobytes per second on a 300-user load.
The product we examined is the company's basic enterprise offering: a five-user copy of its Enterprise Server 5.0.4 that comes with a copy of Netscape's FastTrack server. SCO also includes the National Center for Supercomputing Applications HTTP server with its distribution and, of course, Apache is available on the Internet. We tested the server first with the Netscape server, then with Apache in our two-CPU tests.
Management of the Web server, including setting up E-mail, virtual domains and FTP service, can be done either through Unix commands and configuration files, or by using an HTML Interface with the Netscape browser that is included with the SCO distribution. SCO's online documentation, which measured four linear feet high in the days when printed copies were actually distributed with the software, has been viewable from a Web browser for several years.
The company uses an X-based desktop metaphor for most systems administration and management tasks, even though some of the programs are little more than front ends for sophisticated shell scripts that take care of different parts of managing and configuring the system.
It's worth noting that SCO's kernel-tuning tools are the best of any operating system we examined. Shell scripts and character-based menus allow configuration of every tunable parameter, and the parameters that do require adjusting-most are tuned automatically by the system's dynamic kernel tables-are well documented in the system's online manuals.
For security, SCO offers four levels ranging from relaxed for non-networked environments to a U.S. government C2-certified security that provides access control lists, subsystem authorizations and discretionary access controls, as well as sophisticated features like flushing of secure data from kernel buffers and complete auditing of virtually every system process. Security can be managed either through a graphical interface or a character-based menu interface.
The company has a Kerberos implementation, which is offered as an add-on product; it is not bundled with the base OS, in large part because of export restrictions that would not allow it to be sold outside the United States.
The Enterprise server includes a NetWare gateway that provides file and print services on Novell networks, as well as a proprietary networking product called PC Interface, which provides file and print services to Windows workstations and Macintosh computers. Both services are straightforward to set up and trouble-free to maintain. Optional integration services include SCO Merge, which lets users run DOS and Windows applications on the Unix machine either through an X-Windows interface or on the console, and Windows applications that provide terminal and X emulation services, database connectivity to the SCO server, and even remote administration tools.
The system is the most scalable of any examined in our tests, with support for up to 32 CPUs, four gigabytes of RAM, file systems of up to one terabyte and support for a total of 950 terabytes of storage. It is supported by all of the major relational database makers, including Informix, Oracle and Sybase.
Although its performance in our Web tests wasn't stellar, SCO's Enterprise provides superior fault tolerance, user management and security.
It has a vast and complete feature set, coupled with support for more than 900 server platforms-including 60 SMP systems-and some 2,000 peripherals.
These features, combined with SCO's long experience in putting Unix to work in mission-critical business environments, make Enterprise Server a perfect tool for heterogenous enterprise networks, particularly those requiring the complex mix of tools, utilities and "glue" that SCO offers.
Sean Fulton is vice president of new products for Grand Central Networks Inc., an Internet service consulting firm in Port Washington, N.Y. He can be reached at firstname.lastname@example.org.