I don't know if this is still a problem, but I use ICH10 RAID and installed Slackware in the RAID partition. I modified the "sd.c" file to omit the partition checking on the first two drives.
Change this line.
gd->minors = (index < 2) ? 1 : 16;
The number "2" can be changed and it specifies the number of "sd" device letters to skip. As is it skips "sda" and "sdb". By using a different expression besides "index < 2" it's possible to omit some arbitrary range of letters. This is a KLUGE but was the safest way that I knew to change the code. A driver or kernel parameter to specify devices to skip for partition checking would be helpful.