No matter what happens, the more data that exists, the more likely that it will fail in some way or another. It's a matter of how much total data is being stored, not how it's being stored. If you have 20 hard drives filled with data as opposed to 2 filled with data, its more likely that one of those 20 hard drives will fail then one of your 2 will fail. Data that is spread over multiple hard-drives, however, will be even more likely to be corrupted and ultimately useless due to striping and the fact that the number of files isn't necessarily increasing, simply the size of those files. Therefore, you run into the same problems even if you divide it into multiple hard drives. The only solution is simply to back up the goddamn data in an external drive.