WORM disk drive systems

Write once read many systems use optical disks onto which data is permanently written using a focussed laser beam. At the physical sector level on the disk, data can only be written once and cannot be erased and then rewritten. This is the great advantage of WORM technology for many applications: data cannot be accidentally erased. Many WORM sub-systems, however, are available with `transparent´ software which makes the write once optical disk appear to the operating system exactly like a rewritable hard disk. This means that standard application programs can be used with WORM storage without the need for any software modification. When a file deletion command is issued by the operating system, that file is simply made invisible. Good software packages include utilities which allow retrieval of deleted files and old versions of files. The author looks at WORM systems