Here's my pro Linux software RAID strory:

All my tunes (flac & mp3) are on a RAID-5 array of 6 250 GB drives. When one of the drives died, I replaced it with a 500 GB drive lying around. The broken drive was under warranty, and a replacement drive arrived two weeks later. I forced the 500 GB drive to failed state and inserted the replacement drive, assuming I could just rebuild the array. Then Murphy hit me: a second drive from my array made horrible noise when I applied power. It was dead. Now two drives were faulty and my array would not start, even after switching back to the 500 GB drive. The 500 GB was non-fresh and would not be considered as part of the array. Luckily mdadm had a --force option that would bring back the array to life. All my data was there and intact. I wonder whether any hardware RAID solution would save me in this situation.

Here's my con hardware RAID story:

I once lost a lot of data on an IBM ServeRAID array, where the RAID controller would give an I/O error on a sector of the virtual disk, where every drive that built the array was just fine. Recreating the array solved the condition, but the data was lost.

Pim