When is RAID worth the trouble?
Solution 1:
Don't worry, RAID isn't used throughout the business world because of groupthink! The chance of decent RAID controllers failing is far, far lower than the chance of a disk failure. I don't recall ever seeing a RAID controller fail in real life, while I've seen many a disk die, both in the office and datacenter.
PS: I see your tags. RAID is not backup! :)
Solution 2:
ZFS by SUN (also part of OpenSolaris; Apples OSX - currently read only) not only does raid with various levels but always check to see if the data written to disk is actually there. consistency is key! RAID is useless if you can´t rely on its integrity. Pick a decent RAID controller (I prefer HP´s) and scrub your RAID to find errors periodically.
Softwareraid (as ZFS) on the other hand amkes you more hardware independant if the RAID controller dies and you can´t get an exact replacement.
Solution 3:
Always. Disks are cheap, your information is not. But use software RAID, so you have the flexibility to move forward or change hardware later on (trust me, you will need it). And also use a checksumming filesystem like ZFS, to protect against silent data corruption (which is very likely with large disks nowadays).
Solution 4:
For those of you saying you won't use hardware RAID because if the controller fails and you can't get an identcial replacement your screwed, you're going about it the wrong way.
If uptime is that critical to you, you should NOT be buying cheap hardware. As was said before, use a good raid controller, HP, LSI, Dell etc.
If the controller was purchased from the computer manufacturer, ie Dell server, with Dell RAID controller, Dell will tell you how long they will be stocking those parts, usually this in the in the 4+ year from the EOL of that server.
If having someone running again quickly means you cannot wait for the delivery then you should be purchasing a second spare controller for yourself, regardless of who made it.
If you setup as a RAID 1, you can sometimes take that one of those drives and drop them on a normal controller to recover the data. If that is important to you, confirm/test this with your controller before you are in a critial situation.
Hardware RAID saved my butt 2x. Once in an email server one of the drives failed, I got the email alert from the raid monitoring software on that machine, called up dell and had a new drive the next day, poped it in and it rebuild all on its own. ZERO downtime on that one
Second one, had a drive fail in an old file server that was scheduled for replacement in 6 months. The controller kept it running and we moved the replacement of the server up to that week. Saved buying a new drive (since it was out of warrenty) and again ZERO downtime.
I've used software raids before and they just don't recover as nicely as hardware based one. You have to test your setup, software or hardware to be sure it works and know what to do when the brown stuff hits the fan.