Was he referring to RAID 5? I'm not sure why it would do that, but by the sound of it, it switched from having redundant drives to data striping--essentially the opposite of redundancy. I've heard of switching hot spares resulting in reconfiguration, but not like that. What happens when you put in a hot spare is the data is usually copied over to restore redundancy. You might be in deep **** if it decided to spontaneously change your RAID configuration.