Asciimonster> Erroneus read data cannot be corrected in any way, Asciimonster> so that's all in the game. And that only corrupts a Asciimonster> few files while a complete hard disk crash just Asciimonster> looses you entire info. And if I understand you Asciimonster> correctly, RAID1 *does* protect you againt Asciimonster> that. Moreover the CRC checks on hard disk makes it Asciimonster> report an error before it get's the chance of Asciimonster> reading the wrong info.
I have heard of a case when a cheap hard disk in a RAID1 setup failed, however it didn't report its failure. The hard disk just returned random data. Yes, CRC should protect against this, but it didn't. Maybe the hard disk didn't properly check the CRC. Or maybe it died to such an extent it could no longer control the IDE interface. What happened is a mystery. The computer read this random data from the faulty hard disk (not just file data, file system meta data too) and wrote it to the good hard disk. The result really was all information completely lost.
Note:
1. This didn't happen to me, it is my recollection of events told be a friend.
2. You could argue that it was the fault of the hard disk not returning a failure error code - I agree.
I had a RAID mirror set up for a while on my home Internet gateway/NAT/firewall box. In the end I turned off RAID in favour of setting up a nightly backup onto the 2nd disk with rsync. That way if I accidentally deleted/stuffed up something I could get the previous version back from the backup disk. With RAID I couldn't do that. Sure, I could have backed up my RAID disks but this ain't exactly a mission critical setup and I'd have to buy yet more disk. The way I have it now I can lose 1 day's worth of data, but I could modify the backup regime if that worried me.
I think it's good to question whether RAID is the best solution for a home setup. Sometimes there's a simpler more useable solution that gives you more of what you need for most scenarios.
I'll just go and put my flame suit on now...
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