>>If memory serves, your NAS is being used instead of local storage for your web site(s).
>>
>>If IIS can't talk to its files then sure, it could stop those processes that depend on it. It's equivalent to a hardware failure.
>>
>>That message you report is exactly what I'd expect in that circumstance.
>
>Yes, but I am still wondering why IIS would simply decide to shut the application pool down. Because, the NAS went back online in 5 minutes but it took longer for us to go in VPN, RDP, IIS and all 3-letter acronyms you can find (lol), to start the application pool back.

If the NAS is required for the application pool to function, shutting it down gracefully sounds to me like the secure thing to do. If you have a site that's doing transactions, you can't let them get into an unknown state. It's the equivalent of a C5 error for apps, Windows kills them because something went wrong, in order to preserve other functions of the computer.