Techniques for determining unique ownership of data blocks includes selecting a first data block referenced by a first logical address of a first logical device, wherein first metadata for the first data block includes a reference count and a result used in determining sole unique ownership of the first data block; determining C1, an expected value of the result of the first metadata when the first logical device is a sole unique owner of the first data block; and performing first processing that determines whether the first logical device is the sole unique owner of the first data block. The first processing includes: determining whether C1 equals a current value of the result of the first metadata; and determining that the first logical device is the sole unique owner of the first data block if C1 equals the current value of the result of the first metadata.