When burning a CD or DVD with Windows, you’ll be asked whether you want to use a Live File System or a Mastered disc format. Each has its own advantages and disadvantages.
Windows 7 refers to this as “Like a USB flash drive” or “With a CD/DVD player.” But how exactly can a non-rewritable disc function like a USB flash drive?
A standard writable CD or DVD can only be written to once. When you write data to an area of the disc, that data will be present on the disc forever. You can’t erase this data, except by physically destroying the disc itself.
Rewriteable discs work differently, allowing you to “reset” the disc back to its original state and burn to it again.
Image Credit: John Liu
Mastered Disc Format
The Mastered disc format is the one most people will be familiar with, as it’s been around for much longer. When you use the Mastered disc format, you can only burn to a disc once. This is ideal if you’re filling a disc up with files or burning an ISO image to it.
However, the single-burn restriction applies no matter how many files you’re burning. For example, if you use the Mastered disc format and burn 50 MB of files to a disc, you can’t go back and add more files later. Once a non-rewritable disc is burned with a Mastered format, its state is final. The hundreds of megabytes you could have used are lost – one burn is the limit.
However, the Mastered disc format is more compatible. You can use Mastered discs with versions of Windows earlier than Windows XP and other types of devices, such as DVD players and CD players. These devices don’t usually support Live File System discs.
When using the Mastered disc format with rewritable discs, you’ll have to use an “Erase” operation that wipes the entire disc to delete files. You can’t simply delete individual files from a disc to recover space.
Live File System
The Live File System works differently. Instead of only burning to the disc once, you can burn to the disc multiple times after formatting it with a Live File System. For example, you can have a disc inserted in your disc drive and add files to it regularly. Each file will be burned to the disc as you add it. With a Mastered disc, files you add enter a sort of staging area – they’re not burned to the disc until you click the burn button.
When you want to use the disc with another computer, you can close the session by ejecting the disc. This writes some data to the disc, so you should close the session as few times as possible.
You can later open a new session and burn more files to the disc, creating a new session. However, if you’re using a non-rewritable disc, you can still only write to every area of the disc once. For example, if you burn a 50 MB file to the disc, then delete it later and burn another 50 MB file to the disc, the total space used on the disc is still 100 MB. The original 50 MB you burned to the disc is still present, although it’s been marked as deleted and won’t be shown when you use the disc.
If you’re using a rewritable disc with the Live File System, space used by deleted files will be erased immediately and the space will be reclaimed. This is a big advantage for rewritable discs – you can write to them and delete files as if you were writing to a USB flash drive, without having to perform a clunky full-disc erase operation every time you want to erase some files.
However, Live File System isn’t as compatible as the Mastered disc format. It will work on computers running Windows XP and newer versions of Windows, but many other types of devices won’t work with a Live File System disc.
Ultimately, there’s no one right choice – there’s a more compatible option and a more convenient option. The option you choose should depend on how you want to burn files to the disc and what devices you want to use the resulting disc with.