Application isolation is the process of separating the applications
from the process boundaries and also preventing one application to affect another
and the reducing time that we spend on correcting the issues related to applications.
IIS 6.0 operates mainly in two different application isolation modes.
Worker Process Isolation mode – This mode is quite new and uses
the worker process core component for functioning. This mode is the default
mode for the IIS 6.0 and also it is more recommended. We will see further why
this mode is more robust and secure than the other mode.
IIS 5.0 Isolation Mode – This mode is similar to the Process
model of the previous IIS version.
Let us discuss each mode in detail and also illustrate the factors
on which we can choose the mode. The factors upon which we derive on a specific
mode are listed below.
Performance of the Application after going for a Mode
Reliability of the Application (We need this especially when we go for
Security (We will discuss in next section)
Some of the New cool Features
Compatibility with our application (Last but not the least)
When we consider all the above factors except the last one,
worker process Isolation mode is considered to be the better alternative. The
only issue with it may be the compatibility issues with the legacy
applications. Worker process Isolation mode is also more reliable in the
security aspect. Apart from the above features, worker process isolation mode
also has the support process recycling, multi instancing and the support for
the application pools. Process recycling is the concept by which IIS 6.0
automates refreshing of ASP.Net web applications. By using this approach all
the problematic applications are refreshed automatically and the application
code modifications can be avoided. Overlapping recycling is a special case of
process recycling. In this case the process which is supposed to be recycled
continues to serve all the requests while another process is created in parallel.
As there is an overlap between the same processes it is known as the overlapped
In this scenario we also get to see the concept of Multi
instancing. Multi-instancing is the concept by which we can have 2 or more
instances of the same application. In the overlapped recycling we may have the same
application instances running in different processes. We have a configurable
timeout field based on which we can specify the time for the process to be