policies

• Use par2, and preferably set the redundancy level to 20-100%.
• Always verify the copy is good after writing.

lower-level software

adding parity data

• par2 doesn't support multiple directories, so there are various ways to try to add it
  • sweep
  • par2 the iso, and add to a second session
  • the par2 spec mentions that subdirectories should be possible

verify a backup is good

• if using hard-drive or flash-drive media, first disconnect and reconnect the drive before verifying (because some data can be left in the memory cache)
• if using media that doesn't contain its own read-head (i.e. CD/DVD/tape), verify the data on ANOTHER DRIVE than the one you wrote it on. (often CD drives write data that it's best at reading, but others are slightly less capable of reading)
• tools
  • Windows: md5deep