df -k should show what mount points exist and what disk partitions are associated with those mount points (if this is running a database you may need to find out what raw partitions the data base knows about)
Usuing the format command, you can print what disks and partitions exist.
a comparison of df -k and format and your knowledge of raw partitions should show any free space
I tried to remain child-like, all I acheived was childish.