VOL in general
https://svn.hdfgroup.org/hdf5doc/trunk/RFCs/HDF5/VOL/RFC/RFC_VOL.pdf
https://svn.hdfgroup.org/hdf5doc/trunk/RFCs/HDF5/VOL/user_guide/main.pdf
https://svn.hdfgroup.org/hdf5doc/trunk/RFCs/HDF5/VOL/developer_guide/main.pdf

