Depending on the type of raid setup you have, a raid failure can result in your system coming to a standstill. Unlike conventional hard drives raid drives are prune to many if not a majority of system failures. But as with any system raid too has its loopholes.
In most cases of data loss on a raid drive a software solution would suffice, but be warned that software solutions don’t come cheap. Before even buying particular software solution searches the internet thoroughly and sees if the software really serves your needs. See if the software you are interested in really does what it says because software recovery solutions for a raid setup cost a lot of money.
If the problem is too complicated for a software solution that you may have to hire an expert to do the job for you: Complicated issues such as damage to the setup or the controller can only be fixed physically by an expert. But no matter what option you take both options will cost you a lot of money, so the first step before going in for data recovery will be access if the data is really worth the amount you are going to spend.