After my initial failed foray into RAID arrays, I've avoided them. My issue is that, since I don't often identify problems with HDs right away, the RAID preserves the errors, rather than providing safe backups. Two copies of crap still equals lost data, no matter how fast they save the lost information.
It's not a mater of saving lost information.
RAID is not about "backups" in the traditional sense it's about protection against disk corruption/physical disk failure. All data is written to and read from all disks (you can have raids larger than two disks) simultaneously. Even if one disk goes bad, the data can still be read from the other disk. There is no after the fact copying of corrupted data from one disk to another.
If the raid controller was set up properly, it would take care of everything necessary automatically, including monitoring the disks for failures.
The only way for a raid to loose information is to have the same sector physically corrupted across all disks. The odds of this happening are astronomical.
Suppose a three disk raid.
A file that sits on sectors ABCDE.
Sector A is lost on disk 1, Sector B is lost on disc 2 and sector C is lost on disk 3.
Because you see the whole raid as one drive, the file is still readable in an uncorrupted state because the raid controller will simply ignore the corrupted sectors on each disk reading uncorrupted data from the other disks.
Even if disk 3 suffers catastrophic failure and is completely unreadable, the complete file can still be read. And in the case of catastrophic failure of an individual drive, the raid controller should be alerting you. This should not be something you have to proactively check for.
I do a lot of digital photography. Because of the volume of the files, before I purchased my current computer, I was using a 500GB external hard drive to store my photo data. At the time, CD's were the only backup option and 500GB is a lot of CDs, so I wasn't backing up the external drive.
Then the external drive died. It wouldn't even power up. The only recovery option (which I don't even know if it's possible) would have been to send the drive somewhere to have the platters removed and re-installed in another hard drive to see if the platters were still any good. Even if I could have found somewhere to send it, it would have been an expensive proposition just to find out if the data was recoverable.
I lost years worth of photographs.
Now I use both RAID and on-line backups.
My computer is a custom built machine from a local shop. They set the RAID array up for me, it wasn't something I attempted to do myself.