App gateway + VMSS+ multiple websites

Question

Hello, We are migrating a 2 tier web farm consisting of 100+ websites hosted on IIS, db served by a SQL 2017. The servers continue to host multiple websites in future and the number will increase.

As a target architecture on Azure, we have thought of below
An application gateway serving 2 servers in a VM scale set, which inturn talking to a Azure SQL database. The app gateway is also integrated with WAF policy.
Since app GW+WAF combination allows only 40 rules/gateway and we have many websites to configure, we are forced to create multiple App gateway to meet the overall requirement.

So as a start, we would require 4 App gateway , and as the website number increases , the app gateway number too increases.

Can someone confirm, is this an acceptable architecture? is this going to create problems in future? with more and more app gateways are talking to same set of web servers?
What other things I need to consider/to be aware off?

Please help.

Regards
Thahif

Answer 1

@Mohammed Thahif BK ,

Your setup should work just fine. But keep in mind that the Application Gateway will have multiple instances and you need to check the health of each site before sending traffic to the Web Server. In that case, the number of probes per second on each VMSS instances will be high. Make sure that is not affecting the performance of the server.

Application Gateway also supports widlcard listener where multiple sites can be hosted with single rule and listener.

Regards,
Karthik Srinivas