How safe is it to rely on hashes for file identification?

Question

I am designing a storage cloud software on top of a LAMP stack.

Files could have an internal ID, but it would have many advantages to store them not with an incrementing

Answer 1

Whilst the probability of a collision might be vanishingly small, imagine serving a highly confidential file from one customer to their competitor just because there happens to be a hash collision.

= end of business

I'd rather use hashing for things that were less critical when collisions DO occur ;-)

If you have a database, store the files under GUIDs - so not an incrementing index, but a proper globally unique identifier. They work nicely when it comes to distributed shards / high availability etc.

Imagine the worst case scenario and assume it will happen the week after you are featured in wired magazine as an amazing startup ... that's a good stress test for the algorithm.