1. A method for updates in a storage system, comprising: writing identifiers, associated with data to be stored, to storage units of the storage system; and writing trim records, indicative of identifiers that are allowed to not exist in the storage system, to the storage units; determining whether the stored data corresponding to records of identifiers is valid based on the records of the identifiers and the trim records, and gathering a set of sequence numbers as stored in storage units; determining, from the set of sequence numbers, a latest sequence number that has been acknowledged; and inserting at least one forward trim record that indicates a sequence number later than the latest sequence number is allowed to not be present in the storage system.