In this case the array would have additional M bytes, where M is the number of ghost nodes/cells. But the array has constantly 8 additional bytes, independent of the number of ghost nodes/cells in my files and independent of the number of total partitions.
And the value in those 8 bytes is always (!) zero, which would mean that the node/cell mapped to this value is part of the partition and not of the ghost nodes/cells.
Again, here I wonder where those 8 bytes are mapped to, as each node/cell already has a value mapped to it.