the attached patch adds a level 2 warning when CarpetIOHDF5 cannot read the grid structure attribute (actually a dataset but treated as an attribute) in hdf5 files. This can happen if very old files (pre grid structure version 5) are being read or files that do not have the attribute at all. The attribute is used by the checkpoint recovery routine to reconstruct the process decomposition, but (as far as I know) ignored by the file reader for ID.
There is also one bugfix in 0002 that makes it possible to read multipatch data into a cartesian simulation as ID by using only the cartesian patch. While the patch is fairly simple please comment on whether it is fine to move the calculation of upper/lower into the loop over local maps, given that the upper/lower values are those of the patch to be read from file. The reason for the move is that the calculation needs the stride which is read from the current simulation and not from the patch (and can only be gotten if the map in question actually exists).