The disk space function shows the overall volume of information that you are able to have on a cloud hosting server at a time. With a home PC, for instance, this would be the size of one hdd or the full size of all of the hard disks in the event that the PC has more than a single one. The same way that the space on a personal computer is shared between installed computer software, docs, music files etcetera, the server hard disk space is normally divided between website files, databases and emails. Each file, folder and email message uses a little space on your server, therefore you should take into account multiple factors, not just the size of the files which you upload. For instance, getting large email attachments or running a script-driven site in which the user-generated information is kept in a database also affects the hdd space you are using.