My website (developed in PHP) is currently having 2 sub domains and hosted on the same server hardware. Due to heavy traffic, I want to move one sub domain to another hardware. Is this possible?
Generally domain Name Servers point out to hosting provider DNS entries. If there are two sub domains hosted on two different servers, what are the steps I need to follow to setup like changing "A" or CNAME records and etc.
Yes, it can be done. Change the A records of subdomains to point to different servers. However, web server has to be configured to serve requests for the sub domains.
Try setting up a proxy server such as nginx or lighttpd with virtual domains that point to each of the servers on your local network.
If the two servers will be on two separate public ip addresses, then you can just set it up through your internet registrar (i.e. godaddy), but if they are on the same, make sure you enable wildcard domains.