Werner, you are right, du is not the problem, I restart from the begging again and now it generated without error using -b on compress ( i think using -L -2, also should works). Probrably i did something wrong on the first test. About time using th default script I got 28 minutes and with -b i got 58 minutes (for compress part). I'm using a HP Proliant server with a six core xeon and 20GB of ram and SSA disks.
Thanks a lot for your help.