Wols Lists writes: > When rebuilding a mirror (of any sort), one block written requires ONE > block read. When rebuilding a parity array, one block written requires > one STRIPE read. Again, we're in agreement here. What you keep ignoring is the fact that both of these take the same amount of time, provided that you are IO bound. > That's a hell of a lot more load on the machine. And when faced with a > production machine that needs to work (as opposed to a hobbyist machine > which can dedicate itself solely to a rebuild), you have the two > conflicting requirements that you need to finish the rebuild as quickly > as possible for data safety, but you also need the computer to do real > work. Minimising disk i/o is *crucial*. That is true, it does put less load on the machine giving it more time to perform other tasks, but your original argument was that it is more likely to fail during a rebuild. I suppose if you take the two together and assume the machine is busy servicing other tasks while doing the rebuild, then both are probably going to slow down somewhat leading to the rebuild taking a little longer, but I have a hard time believing that it is going to be 2-3 times longer, or that it is really very likely of having a second failure in that time.
