Irish Wolfhounds need a secure, above-ground fence. They are sighthounds, fast and strong, and accounts involving dogs going through invisible fences with tragic results are heard all too often. A sighthound looks across the horizon to see its boundaries: they should see their fence.
In addition, an invisible fence will not keep other animals or people out of your yard and can result in your dog being attacked or stolen.
An Irish Wolfhound should never be tied or staked out, ever. They are a large, agile hound and tie-out methods are completely unsuitable, giving them only the most restricted of exercise, and can cause injury as well.