By default AutoCAD, creates a back up copy of the drawing every time you save or save as either with the current drawing name or with another name. Every update you’ve done, AutoCAD updates the back up files at the same time.
However, back up files also eats up so much space too. So it likes having two drawings with the same weights of kilobytes at the same time running in your disk. So it is not advisable if you’re working on a disk that has a limited space. Especially, if you saving your work, directly to a removable disk.
By using ISAVEBAK, it improves the speed of incremental saves, especially for large drawings. ISAVEBAK controls the creation of a backup file (BAK). In the operating system, copying the file date to create a BAK file for a large drawings takes a major portion of the incremental save time.
At the command prompt, key-in ISAVEBAK , enter = 0.
ISAVEBAK = 0 (no BAK file is created)
ISAVEBAK = 1 (A BAK file is created)
The only problem you’ll going to encounter if you don’t have any bak files is, you are unable to recover your latest drawing in case of a power failure. So always be sure you save your drawing.