Consider the following scenario.  You have an Internet Information Services (IIS) 6.0 web server running on Windows Server 2003 Service Pack 2.  The Microsoft update KB973917 gets installed on the server.  After installing KB973917, the IIS 6.0 application pools cannot start up successfully.  An inspection of the event logs show that the IIS worker processes are terminating unexpectedly, showing event messages similar to the following:

Event Type: Warning
Event Source: W3SVC
Event Category: None
Event ID: 1009
Date:  12/9/2009
Time:  10:55:01 AM
User:  N/A
Computer: WEBSERVER01
Description:
A process serving application pool ‘DefaultAppPool’ terminated unexpectedly. The process id was ‘1234′.
The process exit code was ‘0xffffffff’. 

Internet Information Services 6.0 may not function correctly after installing KB973917

More Info Here

Best Practices for Configuring FastCGI and PHP

Security Isolation for PHP Web Sites

The recommendation for isolating PHP web sites in a shared hosting environment is consistent with all general security isolation recommendations for IIS 7.0. In particular, it is recommended to:

• Use one application pool per web site
• Use user account as an identity for application pool
• Configure anonymous user identity to use the application pool identity
• Ensure that FastCGI impersonation is enabled in php.ini file (fastcgi.impersonate=1)

For more details about security isolation in shared hosting environment, refer to Isolating Sites with Application Pools.

PHP Process Recycling Behavior

Make sure that FastCGI always recycles php-cgi.exe processes before the native PHP recycling kicks in. The FastCGI process recycling behavior is controlled by the configuration property instanceMaxRequests. This property specifies how many requests FastCGI process will process before recycling. PHP also has a similar process recycling functionality that is controlled by an environment variable PHP_FCGI_MAX_REQUESTS. By setting instanceMaxRequests to be smaller or equal to PHP_FCGI_MAX_REQUESTS, you can ensure that native PHP process recycling logic will never kick in.

To set these configuration properties use the following commands:

C:>%windir%system32inetsrvappcmd set config -section:system.webServer/fastCgi /[fullPath='c:{php_folder}php-cgi.exe'].instanceMaxRequests:10000
C:>%windir%system32inetsrvappcmd set config -section:system.webServer/fastCgi /+[fullPath='c:{php_folder}php-cgi.exe'].environmentVariables.[name=’PHP_FCGI_MAX_REQUESTS’, value='10000']

Note: If those parameters have not been set, then the following default settings are used: instanceMaxRequests = 200, PHP_FCGI_MAX_REQUESTS = 500 (on most PHP builds).

PHP Versioning

Many PHP applications may rely on functions or features available only in certain versions of PHP.

It is a common requirement in a shared hosting environment to support multiple versions of PHP on the same server. IIS 7.0 FastCGI handler fully supports running multiple versions of PHP on the same web server. For example, let’s assume that on your web server you plan to support PHP 4.4.8, PHP 5.2.1 and PHP 5.2.5 non-thread safe. To enable that, you must place corresponding PHP binaries in separate folders on files system (e.g. C:php448, C:php521 and C:php525nts) and then create the FastCGI application process pools for each version:

C:>%windir%system32inetsrvappcmd set config /section:system.webServer/fastCGI /+[fullPath='c:php448php.exe']
C:>%windir%system32inetsrvappcmd set config /section:system.webServer/fastCGI /+[fullPath='c:php521php-cgi.exe']
C:>%windir%system32inetsrvappcmd set config /section:system.webServer/fastCGI /+[fullPath='c:php525ntsphp-cgi.exe']

IIS.net : Learn IIS7: FastCGI with PHP: Web Server For Shared Hosting: Configuring Servers: Preparing the Deployment: Deploying the Windows Server 2008 Platform: Hosting Guidance

The FastCGI support in IIS enables popular application frameworks that support FastCGI protocol to be hosted on the IIS web server in a high-performance and reliable way. FastCGI provides a high-performance alternative to the Common Gateway Interface (CGI), a standard way of interfacing external applications with Web servers that has been supported as part of the IIS feature-set since the very first release. 

Microsoft IIS 7.0 for Windows Server® 2008 and Windows Vista SP1 now includes a built-in FastCGI component. This walkthrough leads you through the steps to use FastCGI module to host PHP applications on IIS7 in Windows Server 2008 and Windows Vista SP1.

IIS.net : Learn IIS7: Using FastCGI to Host PHP Applications on IIS 7.0: Running PHP Applications: Hosting Applications on IIS 7.0

The following articles contain the recommended IIS 7.0 settings to help ensure security and performance in a shared hosting environment.

See also PowerShell Script to configure each of these settings.

In This Section

32-bit Mode Worker Processes

One of the performance benefits of the x64 platform is that it increases virtual address space, making more memory available. We recommend that you configure IIS to use a 32-bit worker processes on 64-bit Windows. Not only its compatibility better than the …

Created Dec 01 2007 by iisteam

Application Pool Identity as Anonymous User

In prior versions of IIS, the anonymous user allowed classic ASP content to be isolated by using a different anonymous user for each site. Isolation was accomplished by preventing ASP scripts from reverting back to the process identity, called the "impersonation …

Created May 09 2008 by walterov

Default Documents

The default document is for client requests to a Web site that do not specify a document name, such as www.microsoft.com. The default document specifies what file to serve. You can configure multiple default documents for a Web site, but there is a performance …

Created Mar 05 2008 by walterov

HTTP Response Cache

The IIS 7.0 output cache is a new feature that makes it possible to cache entire responses in memory, even from dynamic content. Unlike existing caches in IIS 6.0, IIS 7.0 has a “smart” cache, which lets site owners and developers configure the output cache …

Created Dec 01 2007 by iisteam

dynamicIdleThreshold

Introduction When Windows Server® 2008 starts paging heavily (this could be at 1.5x ram), the response time of HTTP requests goes down. This is particularly common in shared hosting scenarios. A new feature in IIS 7.0 allows page file usage (total commit) …

Created Mar 04 2008 by walterov

Dynamic Compression

Dynamic compression can save a significant amount of bandwidth with a tradeoff in using extra CPU. If bandwidth savings are more important than additional CPU, and the server is not currently bound by CPU, enable dynamic compression. The amount of CPU used …

Created Dec 01 2007 by iisteam

Delegated Administration

The IIS 7.0 administrative user interface, called the IIS Manager, offers a new, more efficient tool for managing the Web server. It provides support for IIS and ASP.NET configuration settings. It also lets those who host or administer Web sites delegate administrative …

Created Mar 19 2008 by walterov

Delegating errorMode in httpErrors

There are cases when a hoster may need to delegate to its customers specific settings in the “applicationhost.config” file without delegating the entire section, the errorMode settingin the httpErrors section is one of them, another one is the scriptErrorSentToBrowser …

Created Mar 25 2008 by walterov

IIS.net : Learn IIS7: Configuring IIS 7.0 for Shared Hosting: Web Server For Shared Hosting: Configuring Servers: Preparing the Deployment: Deploying the Windows Server 2008 Platform: Hosting Guidance