You would need to change the backplanes, the two options are; Standard 1x6 BackplaneThe standard 1x6 backplane does not include a daughter card. Only one channel at a time can be utilized for addressing and accessing the hard drives. The ID of the HDDs is determined by the slot. Separate Floppy and CD-ROM connections are also present on this backplane. Split Bus 2+4 BackplaneThe 2+4 backplane is the 1x6 backplane with a split bus module installed. In this configuration, Hard Drives 0 and 1 will be split separate from Hard Drives 2, 3, 4 and 5. So it is safe to say you have the split 2+4 backplane. Sorry i didn't catch that earlier.  
I just populated all 6 hot-swap bays with 300GB 15k Ultra320 SCSI drives and set the 6th drive as a hot swap drive. 2 of the drives appeared on channel 0 and 4 of them on channel 1. All the assigned drive are assigned to logical drive 0. The resulting logical drive is just shy of 600GB (i.e. 2 drives worth) when it should be just shy of 1,200GB (i.e. 4 drives worth...). What am I doing wrong?
Dell 2850 RAID 5 with 6 300GB drives