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    Scaleability is a measure of the ability for an operating system to scale from use on a very small personal computer to a very large network of clusters of high powered multi-processor servers or mainframes.

    The existence of scaleability allows for one kind of smooth growth of a computer system: using the same operating system on the entire intalled computer base. With sufficient connectivity, the same goal can be achieved by intermixing different operating systems at different parts of the scale.

    If the operating system is truely scaleable, it is possible (but not always achieved) to cut administrative, maintenance, and training costs by standardizing on a single operating system.

    If the operating systems used are highly connectable, it is possible (but not always achieved) to choose operating systems at each part of an overall computer network based on their performance characteristics at their assigned tasks. If one’s business includes in-house content creation (graphics, web design, print media, video, etc.), then there will be a need to use a media operating system (such as Macintosh or BeOS) in addition to the mainstream business operating system.

    Even if a company chooses a multiple OS strategy, it is still important to have room for growth, especially on the high end. A company will want to be able to easily expand with additional processors or additional processing units without having to change to a whole new system.

    Windows NT Server is now part of the corporate infrastructure. But according to some IT veterans, NT Server doesn’t belong there yet. NT lacks the robustness, reliability, and scalability found in more-mature Unix, AS/400, and host systems, they say.” —“The Hidden Cost Of NT”w68

    UNIX offers greater scaleability than Windows NT. This not only includes the number of users a single server can support, but the number of microprocessors each OS can handle simultaneously.” — Jim Carr; MicroTimesm1

     Deciding between NT and UNIX is “not a simple decision,” Admits Cyrus Shiva, a partner and vice president of sales for CorpNet Information Systems, a Burlingame, CA, systems integrator that sells both operating systems. Business owners “have to look forward five years, where they’re going with their business, and it requires long-term planning.” —Jim Carr, MicroTimes; Oct 30, 1998m1

    Microsoft has been running a series of television commercials claiming that Windows 2000 can easily connect to other systems and that it is easy to merge operations on separate Windows 2000 systems. Windows 2000 is in fact unable to connect to any other operating system unless the other operating system provides the connectivity (UNIX, NetWare, and the Macintosh provide the ability to connect to Windows). Merging multiple Windows 2000 systems (even just two Windows 2000 systems) is a difficult and time consuming process subject to errors and loss of data. Some businesses have been unable to get a new Windows 2000 system to correctly run their business, even after more than a year of direct Microsoft support.


Reliability and Scalability Graph

—D.H. Brown.w51


     “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.” —Internet Week (Formerly Communications Week) Sept 1, 1997w26


     “Many first-time users are often surprised to learn that most NT servers are capable of running only a single application per machine—be it mail, ERP software, or a custom application. If companies need to scale beyond the 1,500 or so users that Microsoft says the server will support, they must buy an additional piece of hardware and software. Another alternative is to opt for Windows NT Enterprise Edition, which supports eight-processor servers and includes the SQL Server database, clustering, and transaction support. The performance boost that comes with NT Enterprise Edition comes at a price—up to nearly $4,000 more than the standard edition.
    But if you opt for standard NT, running one application per server, you could encounter a proliferation of hardware that must be managed. That’s the complete opposite of the trend in the Unix environment, where IT departments are consolidating multiple applications and users on high-end servers. This centralization of computing resources greatly simplifies maintenance and software upgrades and can reduce support staff requirements.” —“The Hidden Cost Of NT”w68


    “Writing an efficient, scalable mp [MultiProcessing] kernel is not an easy task.” —Orphye74

    “UNIX has produced … extremely powerful multiprocessor server hardware tailor-made to its needs” —Microsoft Windows NT Server 4.0 versus UNIX w51

     While Windows NT supports only four-way symmetrical multiprocessing (SSMC) — that is, four CPUs all sharing equally the computing load — Sun Microsystems’ Solaris version of UNIX can handle up to 64 processors.
     This number might well be beyond the needs of most small businesses, acknowledges Tom Gouge, senior product line manager for Sun’s Solaris servers. But it does show how UNIX offers them as an upgrade path as their requirements grow, he says.
     It also points out the “difference in the Microsoft philosophy and the Sun philosophy,” he says. “As you add more users or applications and you need more computing power, Microsoft’s philosophy is to put in another system — and software license — while Sun’s is to add another processor or memory.”
     Although Solaris is predominantly a “big iron” OS originally designed for the Sun’s SPARC stations and super-servers, the company now sells an Intel-based version for $695, according to Gouge. “We’re finding (Solaris) getting into smaller and smaller businesses,” he says, and a PC-based version is a natural addition to the company’s product line.
    “I think it’s because more of them are depending on these systems to be mission-critical, whether it’s for running their Web sites or e-mail services, or EPR, or they have a branch office that absolutely must ‘talk’ to the headquarters,” Gouge adds. “We see more and more demand for (constant) uptime.” —Jim Carr, MicroTimes; Oct 30, 1998m1

number of processors supported:

     IRIX: 128 processorsw34

     HP-UX: 128 processorse121

     Solaris: 64 processorse64

     SUN-OS: 64 processorse64

     OS/2: 64 processorse122

     OpenVMS: 32 processorse120

     Mac OS X: 32 processorse125

     Rhapsody: 32 processors

     AIX: 24 processors (in the S80 model )e112

    Pyramid: 24 processorse65

     BeOS: 8 processorse82

     Windows 2000 Advanced Server: 8 processorsw50

    ULTRIX: 6 processors (in some models of VAX 6000)e100

     FreeBSD : 4 processors (Intel SMP)e104

     Macintosh : 4 processorse114

     Windows 2000 Server: 4 processorsw50

     Windows NT: 4 processors —Jim Carr, MicroTimes; Oct 30, 1998m1

     Windows 2000 Professional: 2 processorsw50

     Amiga: 2 (one 68060 and one PowerPC)e95

     NetBSD: 1e113

    MS-DOS: 1

    It’s going to take me a while to get all of the operating systems charted and footnoted. Please be patient. Thanks.

    See the chart on number of processors supported.

changing parts

     “Another disk related design flaw in the Microsoft suite of operating systems is its antiquated use of ‘drive letters,’ i.e. drive C:, drive D:, etc. This schema imposes hardware specific limitations on system administrators and users alike. This is highly inappropriate for client/server environments where network shares and file systems are to represent hierarchies meaningful to humans. UNIX allows shared network filesystems to be mounted at any point in a directory structure. A network share can also span multiple disk drives (or even different machines!) in UNIX, thus allowing administrators to maintain pre-existing directory structures that are well-known to users, yet allowing them to expand the available disk space on the server, making such system changes transparent to users. This single difference between the UNIX and Windows operating systems further underscores the original intentions of their respective designers: UNIX was conceived as a client/server operating system for professional use, whereas Windows and its descendents sprang from DOS, an operating system that was never intended to be a player in a client/server environment, much less a server. For more detailed information on this topic, see Nicholas Petreley’s article It will take less drive to make most PC operating systems work like Unix” —John Kirsch, “Microsoft Windows NT Server 4.0 versus UNIX”w51

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    Last Updated: February 24, 2002

    Created: June 5, 1998

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