Data disk is a 420Gb RAID-5 LUN composed by 4 Seagate 140Gb, 10000 rpm, SCSI-3. SCSI adapter is Dell Perc/4DC.
Every Oracle files is under the same directory: datafile, redo, controlfile.
A colleague tell me that it's better to move redo log away from that disk.
And possibly to increase them: now they are 10Mb each.