Hash Code and Checksum - what's the difference?

Question

My understanding is that a hash code and checksum are similar things - a numeric value, computed for a block of data, that is relatively unique.

i.e. The pr

Answer 1

In Redis cluster data sharding, it uses a hash slot to decide which node it goes. Take for example the modulo operation below:

123 % 9 = 6
122 % 9 = 5
141 % 9 = 6

The 6 comes up twice across differing inputs. The purpose of the hash is simply to map an input value to an output value and uniqueness is not part of the deal. So two different inputs that produces the same output is fine in the world of hashes.

A checksum, on the other hand, must differ the output even if one bit in the input changes because its purpose is not to map, but to detect data corruption. So two different inputs that produces the same output is not acceptable in a checksum.