This same method can be used to determine the value of each of the other bits on the removed bit, completely reconstructing the data on that disk. While the failed disk is removed, the data on the remaining disks must be read to reconstruct the data when a disk access is needed. When a new disk is inserted, this method is used to rebuild the data on the new disk, without having to reload the data from a backup tape. When the new disk is fully rebuilt, the data can be read from the new disk. Double Disk Failure Parity does not work if more than one disk fails simultaneously.
Parity only protects against a single point of failure.
CDs and DVDs use a much more elaborate, but analogous, error correcting code to correct these errors. This is why CDs and DVDs must be copied before the number of bad bits build up to a level that exceeds what the ECC can protect from. MS 59 compliments the ANSI X3.131 media error hardware interface standard. The version number of this article is just before the page number below. The website also has articles that provide more details on some of the terms and concepts in this article.