How much disk will you need?

The general answer is a little more than you think. Your virtual system has a full Linux install. This will consume about 1.05 gigabytes. In addition to this, you will need some scratch-space to store items uploaded and downloaded. Finally, you will typically reserve a third of the available space either for generated "file saves" of all or part of your system, or for a partition for real-time snapshotting (if applicable, see the backup section). In addition to the above, Linux processes frequently halt when free-space in any file-system other than the root system falls below 10%

The following is a general table of sizes and usable "production" space: