GuidesIIS vs. Apache, Looking Beyond the Rhetoric Page 2

IIS vs. Apache, Looking Beyond the Rhetoric Page 2

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For some time, Apache and Microsoft have commanded the lion’s share of
the Web server market. While Apache is the clear-cut winner in the Netcraft
and Security Space monthly surveys, Internet Information Server dominates among Fortune 1000 enterprises.

Both are viable choices, and each carries its own set of pros and cons.

With Apache 2.0 in production release since mid-2002 and IIS 6.0 shipping
since earlier this year, we’ve decided the time has come to run a
feature-by-feature comparison of the two servers to help readers better
determine which server suits their needs.


IIS has been an optional component of
the Windows Server operating systems since Windows NT 4.0. Back then, this
was a basic Web server in the form of IIS 3.0. An Option Pack, released
shortly after Windows NT 4.0 was released, included IIS 4.0 and was the
first “real” version of IIS to be used heavily as a Web server platform.

IIS 5.0 was included in Windows 2000 in both the server and desktop
versions, and the updated version, IIS 5.1, is incorporated into Windows XP.
The changes between IIS 4 and IIS 5 are fairly minor.

Windows Server 2003 includes the new IIS 6.0, which is an almost complete
rewrite from the previous editions. It sports a new execution model, better
management facilities, and significantly increased performance.

Apache, on the other hand, has an older heritage, having been originally
based on the httpd code that some would argue started the
entire Web
revolution in the first place. Apache 1.3.x, which was the production
version until 2002, was a largely Unix product that used a number of tricks
to enable it to execute within other operating systems, including Windows.

The production release of Apache 2.0 hit the shelves in 2002. The new
release incorporated a brand-new execution environment that separated the
core functionality of the Apache system from the system that actually
supported and processed requests. Apache 2.0 is now supported under a wide
array of potential operating systems, including all versions of Windows,
Linux, Unix, and Mac OS X, in addition to an array of nonmainstream OSs,
like BeOS and VMS.

Execution Environment

IIS and Apache operate very differently and thus have a variety of
advantages of disadvantages. IIS is obviously designed and available to
work only within the Windows environment. With IIS 6.0, the only platform
currently supported is Windows Server 2003. Although this limits the
deployment platforms for IIS-based Web services, it also provides a number
of benefits, including greater cooperation with the host operating system
and easier management and control through a variety of standard OS tools and

In IIS 6.0, the cooperation between the operating system and the server
is greater than ever. In a change to previous versions, the component that
accepts requests from clients and processes them is now two separate
components. The kernel mode listener, HTTP.sys, listens and accepts requests
from clients, placing the requests into one or more request queues. IIS then
processes the requests in these queues using at least one worker process to
control the execution of the individual requests and applications.

This separate process allows requests to be accepted even when IIS worker
processes aren’t technically running, and also enables finer control on the
worker processes that handle requests. Thus, the admin (or the server,
automatically) can recycle requests to recover from extension and
application failures that would have previously required a shutdown/restart
of the IIS service or, in extreme cases, a reboot of the entire server.

Apache 2.0 was a major rewrite from the previous versions. Among the many
changes, the Web server is now directly available on a variety of platforms,
including Windows. The redesign enables it to support a wide array of
platforms in more efficient ways that lead to Unix- and Windows-specific
execution models that make the best use of the OS.

The core of the system is the Apache Portable Runtime (APR), which
enables the Apache core to run on more or less any system with a C compiler.
A number of multi-processing modules (MPMs) then provide the support for
actually accepting and processing requests. Under Unix, this can be the
traditional “forked” model or a newer threaded model making use of the
threading built into most modern kernels. Under Windows, this also uses a
threaded model, which in some respects is similar to the threaded model used
by the worker processes within IIS 6.0.

Feature IIS Apache
Independent Request Handler Yes Yes
Multiple Process Request Handlers Yes Yes
Thread Support Yes Yes (on a suitable

Dynamic Components

The primary dynamic environment for development within IIS is Active
Server Pages. This is a generic term for a solution that allows code to be
embedded into HTML pages. These ASP pages are parsed by the server before
being supplied to the client as HTML. The ASP system allows developers to
work in a number of different languages, including Visual Basic, VBScript,
JavaScript, Java, and C/C++, along with other open source alternatives,
such as Perl and Python. In addition, IIS continues to support traditional
CGI methods along with its own suite of filtering and execution systems in
the form of ISAPI filters.

Apache is also designed to work with a wide range of languages, either
via the CGI model, or through the use of dynamic modules by directly
incorporating the language interpreter into the Apache environment. This
significantly speeds up the execution of dynamic components for languages
like PHP, Perl, and Python.

Both systems support the Java Server Pages model, and it’s possible to
migrate most JSP applications between the two platforms with few changes.
Other languages can achieve this with varying results. Even ASP can be
supported under Unix through the ChilliSoft ASP component (, through the Apache::ASP module, or the Apache modmono module (

One element that currently cannot be emulated under Unix is the
Microsoft.NET environment. IIS 6.0 and Windows Server 2003 make heavy use
and provide excellent levels of integration with the .NET Framework.

Feature IIS Apache
ASP Yes With Chilisoft, Apache::ASP, or modmono
CGI Yes Yes
Perl Yes Yes
Python Yes Yes
PHP Yes Yes
JSP Yes Yes
.NET Integrated Yes No

Original date of publication, 09/09/2003.

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