The technique introduced here involves using a block address and a corresponding generation number as a “fingerprint” to uniquely identify a sequence of data within a given storage domain. Each block address has an associated generation number which indicates the number of times that data at that block address has been modified. This technique can be employed, for example, to maintain cache coherency among multiple storage nodes. It can also be employed to avoid sending the data to a network node over a network if it already has the data.