Yes, the drives are hot-swap.  If the drives are accessible from the outside of the machine, they are always hot-swappable.  If it's hot-swap, swap it hot.
I've got a 2850 PowerEdge server.  I've got to replace one of the hard drives.  I know that server has a RAID-5 array.  Can I hot swap the failing HD?
Is the HD's hot swappable on a 2850?