A system and method for performing read optimization of a volume while allowing user operations to target the volume. Read optimization is prevented from being performed for a top level of the medium graph for a given volume, wherein the top level is in a read-write state. Rather than waiting for the given volume to be idle so as to perform read optimization, read optimization is run at lower levels in the medium graph of the given volume. This allows user operations to modify the medium graph of the top level of the given volume while simultaneously read optimization is being run on mediums which underlie the top level.