Put pilot logs in subdirectories
Currently, we drop the pilot logs in the entry directory. The number can get pretty high -- more than 25k files per directory. Even with dir_index, ext3/ext4 don't necessarily perform very well in this case.
We could create subdirectories, either keyed on the last digit or two of the cluster number, or by timestamp. This would affect other things downstream though -- external, log parsing, APFMon linking, and so on.