Barry gave you a lot of good advice with those articles. One of the best options is a NAS (network attached storage) server as they are relatively inexpensive, provide easy access to your data without messing with connection and power cables, and your data is backed up (via a parity disk) in case one of the drives fails. Lime Technology sells 40TB server for $1,100 if you go here http://lime-technology.com/sb/, which includes everything but the hard drives, which you can add as your needs grow. For the 18TB, you'll need to invest about another $1K for the NAS HDD drives. Other NAS solutions I would look at are Synology's 8-bay Disk Station http://www.amazon.com/Synology-DiskStation-Diskless-Network-Attached/dp/B0078RETQE%3FSubscriptionId%3DAKIAICE7LOAJMK3SSLPA%26tag%3Dp00935-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D165953%26creativeASIN%3DB0078RETQE
and the Drobo B800FS http://www.droboworks.com/Drobo-B800FS.asp.
Like Barry says, these don't need to be on a shared system, even though they are often used that way within an office environment.