Creating error correction files
Archival

Tips for archival of error correction files

Nothing is wrong with doing so, but be aware that your data and protective error correction files are kept on media with equal reliability. When you encounter read errors on a data medium it is likely that the medium containing the respective error correction files has also gone defective. After all both media have been written at the same time, and they have the same aging characteristics.

Therefore it is important to protect error correction files just as if they were normal data. To be more specific, the medium containing error correction files must be protected with error correction data as well. Here are two ways of doing this:

1. Storing error correction files on separate media:

   Use additional media just for keeping the error correction files. If you use no more than 80% per medium for error correction files it can be augmented with error correction data. This allows you to recover the medium if you run into problems reading the error correction files at a later time.

2. Storing error correction files on the next medium in sequence:

   Maybe you are using media for an incremental backup strategy. In that case you could collect files until the first medium can be filled. Write that medium as usual and create an error correction file for it. Include that error correction file into the backup set which will go onto the second medium. When the second medium has been written, write the error correction file for it onto the third medium and so on. This way all media in the chain are protected with error correction files (with the ecc file for the last medium residing on hard disk until another medium is written).

   Of course Murphys Law may strike and result in all media of the chain becoming defective. In that case you need to recover all media, starting with the most recent one ;-)