RE: R710 error while booting: pcie training error integrated RAID
The Poweredge R710 is one of our 11th generation servers, where as the H710 is one of our 12th Generation controllers. So the problem is that the controller you have installed isn't compatible with that server. With the R710 you would need the H700 controller (512m cache = part # 1THG8, 1GB cache = part # G5V20) to use in that model server.
Now in regards to the error, it looks like the combination of hardware (memory+CPU's+ other devices) is exceeding the ability of the power supply. Try taking the server down to the minimum memory and see if that error clears, as well as if the iDrac is accessible. If so then you may want to consider upgrading from the 570W power supply up to the 870W (part # 3257W), to help alleviate the issue, or you would need to lower the amount of memory till the error isn't reported.
Let me know if this helps.