Apache v/s IIS

APACHE v/s IIS

Every website needs Web server software in order to process requests and deliver data and choice software either Apache or IIS.

Apache HTTP Server

The Apache HTTP server is an open source Web server application developed by the Apache Software Foundation. The server software is freely distributed, Most suited operating system would be Linux (which is also Open Source Operating system) even it comes with windows version.

Most PHP based web applications prefer apache over IIS and if you want ASP.NET web application in Linux us hard task (You have to go Mono instead .NET Framework)

Multi-processing modules (MPMs) provide the support for accepting and processing requests through traditional “forked” model or threaded model in UNIX. For Windows, this also uses a threaded model, almost similar IIS 6.0.

Microsoft Internet Information Service

Microsoft’s IIS is the next most popular Web server after Apache. It enables services like File Transfer Protocol (FTP), Hypertext Transfer Protocol (HTTP), Simple Mail Transfer Protocol (SMTP) and others that enable a Windows machine to manage Web sites. The latest version also includes various modules for security, filtering, caching, ASP.net integration, compression, redirects, logging and diagnostics.

Because IIS is provided for Windows systems only, the choice to use IIS necessitates the choice of a Windows Server, and therefore increases running costs. Windows is also prone to more malware attacks, and has a reputation as a less secure server option. IIS offers in-depth diagnostic tools such as failed request tracing, request monitoring and runtime data.

All requests from clients and processes handled through two components. 

Kernel mode listener and 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 thus Admin can recycle requests instead of reboot.

Executing Environment	IIS	Apache
Independent Request Handler	Yes	Yes (limited)
Multiple Process Request Handlers	Yes	Yes
Thread Support	Yes	Yes (on a suitable OS)

Language Components	IIS	Apache
ASP	Yes	Apache:::ASP or mod mono
CGI	Yes	Yes
Perl	Yes	Yes
Python	Yes	Yes
PHP	Yes	Yes
JSP	Yes	Yes
.NET Integrated	Yes	No

Systems support encryption technology in SSL, and can be used with IPSec implementations and IPv6.

Security Authentication	IIS	Apache
Secure Login	Yes	Yes
SSL	Yes	Yes
Basic Authentication	Yes	Yes
Digest Authentication	Yes	Yes
LDAP Authentication	Yes	Yes
Active Directory Authentication	Yes	Only with third-party modules
Passport Authentication	Yes	No

Performance measurements is a difficult job though running IIS and apache, as it all depends on configurations and design you doing with the system

Performance Features	IIS	Apache
In-Memory Cache	Yes	Yes
On Disk Cache	Yes	Yes with mod_file_cache
Built-In Execution support	Yes, with a suitable ISAPI filter	Yes with suitable modules
Cached Execution support	Yes, with ASP/ASP.NET	Yes  with mod_perl and others

Support Model	IIS	Apache
Text File Configuration	Yes, through XML Metabase	Yes
Command Line Management	Yes	Limited
Remote CLI	Yes	Yes
Web-Based Management	Yes	Yes, through Webmin and others
GUI-Based Management	Yes	Yes, through Comanche and others

to conclude.......

Apache	IIS
More than 60% of Information websites	20% of information websites
Supported in Unix, Linux, Windows, OS/2	Supported with Windows
Apache is modular in structure, permitting Apache users to pick and choose modules to fit their requirements	ability to customize IIS functionality is limited
LAMP – Linux + Apache + MySQL + PHP ( Free and Open Source s/w )	WIMA - Windows + IIS + MS SQL +ASP.NET (Not Free and Closed s/w )
LAMP combination is lot cheaper as there are no licensing costs.	IIS and Windows are licensing will be an added cost, potential lock in to Microsoft products

Please feel free to correct me, you comments are most welcome.