thx Joseph. Its what i supposed. scsi device are map in /dev/sg device in the same order which they are plugged. I supposed that the last number in /proc/scsi/ide-scsi/0 and /proc/scsi/sbp2_0/1 file path is the nuber on /dev/sg<number> But in fact i wil not use /dev/sg only /dev/sd (wich are only hard drive) Thx again Xavier