What do you do when Hardware fails? If you work in IT support you know this.
So the most important thing when you're dealing with hardware fails is to have a plan of action in place beforehand if you have mission-critical parts, like raid controllers or network card, make sure that you have spares in all of those.
Always keep a few spare drives on the shelf. Make sure that they are the same speed, same size, same cache. Make sure the replacement is usually from the same manufacturer as well.
And always have a backup on hand.