Report on the cost of having many files (empty)

Summary: we want to stay at three levels of nesting (aaa, aab, aac, ...)
The cost is still acceptable (on my Mac SSD), 11seconds, while one level more
becomes very expensive (>3 mins just to create the files)

###########################
4 levels: up to 65536 files
###########################

pizzi@swissmongoose:~/tmp/test$ time ./create.sh

real	3m9.568s
user	0m59.093s
sys	1m41.880s
pizzi@swissmongoose:~/tmp/test$ time rm -r data/

real	0m4.944s
user	0m0.135s
sys	0m4.351s
pizzi@swissmongoose:~/tmp/test$ mkdir data


##########################
3 levels: up to 4096 files
##########################

pizzi@swissmongoose:~/tmp/test$ time ./create.sh

real	0m11.057s
user	0m3.609s
sys	0m6.040s
pizzi@swissmongoose:~/tmp/test$ ls data/ | wc -l
    4096
pizzi@swissmongoose:~/tmp/test$ time rm -r data/

real	0m0.259s
user	0m0.008s
sys	0m0.234s
