Specifically, the reason for the multiple disk requirement is the Real Time Duplication feature. This feature specifically writes out all copies of the files, to the disks in the pool in parallel.     The reason this is a big feature is that when a program opens a file, it locks it. That means it can't be moved, copied or otherwise altered while the file is open. This includes data on the pool, and definitely affects the ability of our software to duplicate the data.  And why does this matter