I recently upgraded my gaming rig from AMD to Intel and had boatloads of problems with the Windows OS finally requiring a complete reinstall.  Now I am thinking about upgrading one of my two unraid servers from an older Intel i7-8700 to the AMD Ryzen 5900x I pulled from my gaming rig (moving to ddr4 ram, pci gen 4 bus, and of course the entire chipset and cpu are significatly different than the Intel setup).  Am I going to run into any major issues if I just plug the USB in from the current server into the new server after transplanting the hardware?  Am I better off starting fresh and transferring my license from the old install to the new one?  Can I even do that, and if so what do I have to do before tearing down the old server?

Short answer: If you are just swapping the CPU/MB/DRAM, then it is no problem at all.

 

Long(er) answer: If you have VMs, expect to do some reconfiguration (and possible reinstall) of them.  As far as the array and cache, unless you have odd HBA controllers that are being changed, all of the drive configurations should just boot up configured as before.