Hello everybody ! Thanks for all the advices, iI will try all theses new values, and i'll post my final values on this thread. About the benchmark and the results, i dont know if can publish values about Oracle performance ? For MySQL and PostgreSQL, i think there is no problems. Just a last question about the pg_xlog : i understand that the directory must be moved but i have just 3 disks for the database : disk 1 and 2 for the data, disk 3 for the indexes, where can i put the pg_xlog ? OA.