Not true with mdadm. Yes, your unreadable single byte will translate into a corrupted file somewhere, but I've recovered plenty of mdadm RAID5 and RAID6 arrays that had lost one or both extra drives and suffered from UREs on the remaining disks. Love good software RAID!
I agree about software RAID – I use it exclusively myself. Also, nice to know that an array can be recovered, even though it would seem to be a reasonable thing to assume, it is good to know that it is possible.
But my point was that:
1. You still have some lost data.
2. An RAID5 array which breaks in this way must be manually rebuilt, possibly from a rescue boot media. Your server will no longer even boot up by itself.
