Many people think that RAID configuration can protect their data for sure. This is not the case because even RAID 1 have its own problems. The most common problem that many server operators face is that after a drive fail, the rebuilding process take the other functional hard drives to the maximum limits sometimes causing one of them to fail. This is often true in RAID 5 and when you end up with two failed drives, all the data will be lost on the array.
Another common cause of RAID failure would be the RAID controller failure. If the RAID controller failed and you are unable to find the exact same controller with exact same specifications and/or the RAID controller you have now do not have a the capability to recover data in case of a controller failure without losing the data, (MOST controllers rebuilt the RAID array when a new controller is added) you will lose all the data on your system.
The lesson here is that we should always backup important data on more than one computer. If you have important data such as company information or any mission critical data, then you should also back up in more than one physical location. For example, if you have data that must be protected at all cost, it should be back up outside of the house that the main server is located. This will safe guard the data in case of a fire or massive failure in electrical system causing a power surge that didn’t suppressed by the UPS.