I'm currently building an home server. I'm using an Intel Pentium G3220 CPU. I want to configure RAID 1 for the two 3TB Western Digital WD30EFRX Red HDD in the server. My question is if software RAID (under Ubuntu Server 14.04) would be a good idea or would it take too much CPU performance?
Software RAID1 cpu requirements are pretty much none.
You won't notice any problems. It's most likely that you will encounter disk IO problems first (depending on the usage) due to RAID1 needing to write to both disks before acknowledging the IO.
Other than that I believe that especially for home use you won't notice any performance issues related to sw-raid1 and cpu.