I'm not familiar with Mepis but I'm guessing that it starts up like (almost) every other Linux. I mean that it's not like Sentry Firewall CD that starts up using PHP scripts. The fact that it's a fresh install eliminates things like udev remapping the device.
One thing that happened with a recent installation of OpenSuSE that may relate to this. I installed OpenSuSE with a USB disk drive and a USB mouse attached. This caused a problem with the installer incorrectly mapping the cdrom drive to a SCSI address. I wonder if you had any USB devices attached while you were installing Mepis and if that would have affected your initrd configuration.
Other ideas are the same old same old. Run lsscsi and lspci. If you have the hwinfo utility then run that. Pipe the output to a file and read it using less. Look in the /proc directory. Here are some ideas on that. I don't have any SCSI disks so I probably don't have the same directory structure as you.
ls /proc/scsi # I don't have a /proc/scsi but you might.
Well, you get the idea. If I had any SCSI disks I could identify pertinent files but I figure where you see an ide directory you will probably also see a scsi directory in the /proc and /sys trees. The pseudo-files in there can be informative.