As mentioned in this blog http://technet.microsoft.com/en-us/library/hh389760.aspx it is possible to have multiple instances of Reporting Services on the same computer. This is meant in situations to support development and production installations of Microsoft Dynamics AX, or to support multiple production installations of Microsoft Dynamics AX.
When there are different instances of Reporting Services for AX2012 the load is not spread over these instances therefore not allowing for high availability or scaled out deployments. We have seen recently some questions on how this should be done when there is a high load of SSRS activity and one SSRS instance is not enough. The answer to this to cope with a high load is to use SQL Reporting Scale-out deployments. As described here:http://technet.microsoft.com/en-us/library/dd309577.aspx In Summary here are the steps you need to use scaled out deployments with AX2012:
For SQL Reporting Scale-out deployment you will need Enterprise edition instead of Standard. Full details on configuring SQL reporting Services is detailed on TechNet: How to: Configure a Report Server Scale-Out Deployment (Reporting Services Configuration)
• First you need to set up your Report server in Scaled out deployment. Basically the means you are connecting multiple SSRS Reports servers against the same SSRS database. When you deploy reports in a scaled out environment the reports will appear on all SSRS servers that are installed in this scaled out deployment, after you have deployed them on only one SSRS server
• Be careful that your reports does not require any other components installed on the server. If so, you must make sure that this external component is properly installed on all servers.
• Now you need to create an Network load Balanced (NLB) cluster in front of these servers. You can do this with Windows NLB or with a hardware NLB switch. You must configure your AX report server to point to this NLB address. Know when a client, EP, Role center or anyone else enters the URL for the NLB cluster the load balance will happen according to the rules for the NLB cluster
• By now you have created a NLB cluster that will load balance your reports, but be aware that you also need to do this for the AOS servers. The AOS Cluster load balance mechanism will work when you access using RPC on port 2712..2811. But reports are executing using services that uses WSDL on ports 8101…8200. The WSDL ports are NOT part of the AOS cluster, a similar NLB cluster must be created in front of the AOS in order for these server to respond as load balance. See Configuring network load balancing for services [AX 2012] for more details