Data backup is an often misunderstood part of the recording process, but arguably one of the most important.  A recording studio is responsible for supplying you, the client, with our services, be it recording, mixing, mastering, etc, and a finished product, a mixed and/or mastered stereo recording.  What happens to the original multi-track recordings is up to you.  We don't store your multi-track data on our drives indefinitely; in fact it is common practice to reformat these drives on a weekly basis to keep them in prime working condition.  We strongly recommend that you plan your data backup prior to your next recording session; this backup will enable you to edit and/or remix your project at any time at a future date. A stereo master is not sufficient as a backup, as it is impossible to completely isolate any one instrument off of a stereo mix if something needs to be edited or reworked.  Short, one-time sessions can be backed up onto a DVD-R or CD-R, depending on the amount of data that you have.  A firewire hard drive is the best option for long-term projects spread out over several sessions as well as anyone who plans do more recording in the future.  Since backup time is usually billed at the standard studio, hourly rate, the firewire drive would certainly be the fastest and most cost effective.  When planning your recording budget, please be sure and give proper consideration, and work into your budget, a means of backing up.  At the end of the day, you've invested your time and money into your music, please secure it.