A client identifies a first data unit to be shared from a first file to a second file and sends an operation to copy that indicates the first data unit to be shared. The operation to copy the first data unit from the first file to the second file is received. In response to receiving the operation to copy the first data unit from the first file to the second file, it is determined whether the first data unit can be shared with the second file. In response to determining that the first data unit cannot be shared with the second file, the first data unit is copied to the second file. In response to determining that the first data unit can be shared with the second file, the first data unit is shared between the first file and the second file.