I had 1 4TB drive on its own that is quite full, now I got 2 additional 4TB drives, and I want to use the three in a raid5 configuration with some kind of software raid, like lvm or zfs.
But I don't have anywhere to keep the data from the original drive while I make the array. Is it possible to make the new volume keeping the existing data? Or, is it possible to make a raid5 with 2 disks originally, copy the data, and add the original drive afterwards?