What are the different levels Of IIS isolation? 

The IIS consist of 3 level of isolation as shown below:-

LOW (IIS process):- In this type of isolation the main IIS process and ASP.NET application run in the same process.If any one crashes the others  are  also affected. e.g.  let's say (well this is not possible) I have hosted  Google ,  yahoo,  .amazon and hotmail  on a single PC. Hence  all application and the IIS process runs on the same process. In situation  any website crashes it affects every one.

Figure: -LOW IIS process scenario

Medium (Pooled):- In the Medium pooled isolation the IIS and web application run in different process. In this case there are two processes process1 and process2. In process1 the IIS process is running and in the process2 we have all the Web application running.

Figure: -Medium pooled scenario

High (Isolated):-In the high isolation scenario every process is running is their own process. In the figure below there are 5 processes and every one handling individual application. That consumes heavy memory but has highest reliability.

Figure: - High isolation scenario