How does the probe handle symbolic links?
The probe ignores symbolic links. Thus if it is scanning a directory tree and encounters a symbolic link to some other area in the file system, it will not follow it.
How does the probe handle hard links?
The probe attempts to detect if two files in the tree it is scanning point to the same data and automatically ignores the duplication.
How does the probe handle sparse files?
By default the probe is not aware of sparse files. This means that it will read zero values for the sparse regions of the files, which can result in artificially high data reduction. The probe reports zero chunks to hint at this potential issue. Refer to Understanding VAST Probe Output for more details. Note that the probe can be run to recognize sparse files on some files systems as described in the document just referenced.
Can the probe scan multiple unrelated directory trees?
Yes it can. This is done by providing multiple --input-dir values.