RAID arrays, that is a redundant array of independent disks can fail for many reasons as with any hard disk system, a simple control or emulator file can easily deny access to all or part of the information stored on a raid array. This is particularly common when using RAID 5 systems. Some of the better data recovery software companies offer programs that will assist you to recover RAID 5 array data. This data can be stored as a disk image and then reinstalled onto the RAID system after it has been rendered operable.
Some RAID 5 recovery software offers a more refined solution in that they will scan and copy RAID information from an array and create on a larger hard disk drive a virtual RAID array. This allows data access until your array can be placed back online. When searching for a program to recover raid 5 array information, bear in mind that this is an extremely specialized process and you will need a data recovery tool targeted exactly to this purpose.