Logs are in /var/log/messages. You can read last start messages (among other things - SCSI start) and see if everything looks correctly.
How are the devices named when you have many controllers? IMHO, when you have 6 devices, 2 controllers, every controller with 3 devices it's:
devices connected to 1st controller: /dev/sda, /dev/sdb, /dev/sdc
devices connected to 2nd controller: /dev/sdd, /dev/sde, /dev/sdf