Very.
Parity raids are best used with enterprise disks, like WD RE4, HGST Ultrastar or Seagate Constellation disks. Some consumer disks like the HGST Deskstar and Samsung F1/F3 are known to work pretty good as well, but WD Color disks (black, red, green, etc.) are well known for their TLER problems and are not suitable for parity raids.