The 3.5 year old steps are equally valid today for many and probably most cases. Been there done that and I'd never do it again; the cost of the hard drive isn'

The 3.5 year old steps are equally valid today for many and probably most cases. Been there done that and I'd never do it again; the cost of the hard drive isn't worth the blood pressure and strong drink this kind of juggling causes. IFF the machine was set up with LVM (and there's a single VG with the right properties) you could build the MD array degraded, add it as a PV under LVM and migrate the data at that layer[0] then nuke the old drive and add it to the array. I believe you could even do it without rebooting but I've never tried. Additionally, making distros boot from LVM isn't always straightforward, at minimum you'd probably have to get your hands dirty with grub. That said both BTRFS and zfs are (theoretically) "windows easy" for this case, once you're booting from them you can add mirrors to your heart's content and things should Just Work. [0] http://www.greyoak.com/lvmdrive.html http://www.greyoak.com/lvmdrive.html