A library virtualisation module (LVM) 13 is disclosed, the LVM being configured to connect first and second hosts 11, 12 to a library 14. The LVM comprises least two host input/outputs, each for connection to a respective host; and a library input/output, for connection to the library 14. The LVM 13 is arranged to modify requests received at its host input/outputs and to provide modified requests to the library input/output in such a way as to divide resources of the library 14 between the hosts 11, 12 without requiring unmodified requests to take into account the division of resources.