Hi @AJF ,
To prevent server goes down and make IIS highly available, I would recommend you to use load balancing and create an IIS farm.
IIS ARR will automatically detect if a server in the server farm is available and proxy the request to a healthy server if it is unavailable.
Configure health check monitoring
If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.
Best regards,
Bruce Zhang