I have 2 sites: site.com and us.site.com
site.com (18.104.22.168) is hosted in Asia and us.site.com (22.214.171.124) is hosted in USA
The majority of the visitors located in USA go to us.site.com
A few visitors located in USA and using site.com are directed to us.site.com with code using GeoIP location.
The problem is when the site.com fails those few users get an error.
I may use 2 A records for site.com (126.96.36.199 and 188.8.131.52) to overcome this problem but in this case lots of visitors (may be the majority) located in Asia will be redirected to 184.108.40.206 depending on the browser behaviour.
I can redirect the Asian visitors to 220.127.116.11 with code but this solution is very inefficient.