You should not leave valuable work on your computer's hard drive without making a backup for 3 reasons ...
The comparative robustness of computer storage technologies is ...
Your basic options are ...
This writer uses CD-RW and creates incremental backups from dated folders.
Cheap unbranded blank discs are cheap for a reason. If you have critical data you should consider using good branded CD-R, DVD-R discs. Is it really worth trusting weeks of work to a disc that cost 10p?
Whatever discs you use, remember that data burnt on a computer optical drive is stored by using a laser to change the colour of a light sensitive surface, unlike commercially pressed optical discs which have physical pits and lands stamped into an alloy layer. Your data may become corrupted if the disc is exposed to strong light and the long term integrity of discs burnt rather that pressed in a factory is untested. Consider cloning discs every 2-3 years.
You can burn to internal optical drives at high speeds but, do bear in mind that the faster you burn the more likely it is that disc errors will occur. Many sound engineers burn red book CD master discs at no more than 2x for this reason.
Also be aware of the following ...
If you burn a disc from data stored on a network drive , the data flow may be interrupted during the burn and your disc will fail. It may therefore be a good idea to transfer large data files to a local hard drive before burning.
If the data is severely fragmented (spread all over the hard disc surface) you will need to burn at a slower speed. This can happen with audio files after a heavy multi-tracking session with Pro Tools or Cubase for example.
If you are burning work using a USB1 connected drive (which is a relatively slow interface whatever actual drive mechanism the case contains) keep to 2x speed. The USB connection is unreliable at faster speeds.
FireWire, USB2 and SCSI drives will operate without any problems at between 8x or even 16x.
Disc-at-once mode (DAO) writes a disc in a single uninterrupted pass of the laser and "closes" the disc so no data can be added to it. If it is a CD-RW disc it can be erased (all previously burnt data will be removed) and used again.
Disc-at-once mode is required for writing in the red book audio CDs format (to be played in a regular CD or DVD player). This format requires the disc to be burnt in one pass with one table of contents. The disc is then "closed" and no additional sessions can be burnt to it.
Roxio Toast's "Advanced" dialogue box showing the correct settings for a red book audio CD.
Burning in (multi) session mode leaves the disc "open", allowing for more data sessions to be added at a later date until the disc is full.
When burning incremental backups of computer data, (multi) session mode should be used, unless the total amount of data to be brunt is near the capacity of the disc. The common method is to place all data to be burnt in a named folder ("Backup 12/7/2004" for example) and for this folder to be burnt as a session.