1. A method comprising: receiving first, second and third write requests directed towards a logical unit (LUN), the first, second and third write requests having respective first, second and third data, the first, second and third write requests representing respective first, second and third offset ranges of the LUN, the second and third offset ranges overlapping the first offset range, the write requests processed at a storage system having a memory; associating first, second and third keys with the respective first, second and third data; storing the first, second and third keys in respective first, second and third entries of a metadata structure; merging the first, second and third entries to form a fourth entry, the fourth entry representing a merge of the first, second and third offset ranges, the second and third entries stored on an array of storage devices attached to the storage system; and storing the fourth entry on the storage array.