see the other responses to address the solr/best practices aspects of your sitaution, but as to the specifics of why you are seeing what you are seeing:
your shell (regardless of wether you are on a unix box or a windows box) has toresolve the "*.xml" part of that command line and convert it to the "real" list of all files in a directory ... with more then a few thousand files that will take a non-negligable amount of time anyway -- let alone when you get to the millions. this is why you might notice a considerable pause before the SimplePostTool ever logs anything ... it hasn't even been run by your shell yet (not to mention that once your shell finally does execute the java process, the JVM has to initialize an array of those million filenames before it ever calls the "main(String[])" function of th SimplePostTool) -Hoss
