I have LVM set up on my server and i am going to remove a hard disk. When i use the command..
..will this simply copy the data over to the other disks or does it wipe out data as its being copied over?
pvmove leverage's LVMs ability to create mirror LVs. The first thing it does is set up a temporary LV mirror for each LV on the original PV. Then it syncs the mirrors the LV at the block level, I believe one at a time. Once a LV's mirror is in sync the mirror on the original PV is then removed.
A few standard references for pvmove.
And, a short article at hackery on pvmove Disk Migrations