Partition question: Device not configured?

IDS2000, RedHat Linux 6.1, kernel 2.2.12-20smp. I have 52G of RAID0+1 space. I used cfdisk to create 2 primary partitions (for user filesystems) and the remainder is divided into 2G logical partitions to be assigned into dbspace as needed. I've read a lot about raw/cooked filesystems in Linux and LVM considerations, but for time being, I'd like to just use plain devices. My problem is that only the first 6 partitions are usable. When I try to assign any of the rest, I get the error message, "Device not configured" (I used mknod to create /dev entries for sdd16-25). Is there a step after partitioning that I've omitted? Is it possible to have so many logical partitions? All suggestions much appreciated. -- Carrie Coy output of fdisk: Disk /dev/sdd: 255 heads, 63 sectors, 6692 cylinders Units = cylinders of 16065 * 512 bytes Device Boot Start End Blocks Id System /dev/sdd1 1 1216 9767488+ 83 Linux /dev/sdd2 1217 1581 2931862+ 83 Linux /dev/sdd3 1582 6684 40989847+ 5 Extended /dev/sdd5 1582 1824 1951866 83 Linux /dev/sdd6 1825 2067 1951866 83 Linux /dev/sdd7 2068 2310 1951866 83 Linux /dev/sdd8 2311 2553 1951866 83 Linux /dev/sdd9 2554 2796 1951866 83 Linux /dev/sdd10 2797 3039 1951866 83 Linux /dev/sdd11 3040 3282 1951866 83 Linux /dev/sdd12 3283 3525 1951866 83 Linux /dev/sdd13 3526 3768 1951866 83 Linux /dev/sdd14 3769 4011 1951866 83 Linux /dev/sdd15 4012 4254 1951866 83 Linux /dev/sdd16 4255 4497 1951866 83 Linux /dev/sdd17 4498 4740 1951866 83 Linux /dev/sdd18 4741 4983 1951866 83 Linux /dev/sdd19 4984 5226 1951866 83 Linux /dev/sdd20 5227 5469 1951866 83 Linux /dev/sdd21 5470 5712 1951866 83 Linux /dev/sdd22 5713 5955 1951866 83 Linux /dev/sdd23 5956 6198 1951866 83 Linux /dev/sdd24 6199 6441 1951866 83 Linux /dev/sdd25 6442 6684 1951866 83 Linux