hi all i am running out of disk space at a machine. the machine can't go down for a long time. since its running for a yeah now.

and is working for lots of people. i have added a disk of 250 gb and rebooted.
the server show up the drive in the startup but does very litle with it.
do i have to mount it or something to get it activated to use the space i need so hard..
can anybody help with some info or a guide..