It would be good for Obnam to optionally be able to verify that hash collisions do not happen. This requires downloading the data with the same hash, and comparing the bytes, which can be quite expensive. However, backup programs should be reliable, and the user should be able to choose reliability over speed.
Three modes are needed:
- assume hash collisions do not happen (deduplication, max speed, max risk)
- verify that hash collisions do not happen (deduplication, no risk, performance hit)
- do not deduplicate (max speed, no risk)
--liw