Yes, I did try to boot off a 4.5TB device. Now, the individual partitions are:
/ 1GB /dev/sda2 ext3 /boot 250MB /dev/sda1 ext2 (Marked as primary partition.) swap 1024 /dev/sda3 ext3 /data 4.449TB /dev/sda4 ext3
All 9 drives are RAID5 together via the 3Ware card. Tomorrow, I'll don my earplugs and create a small 1TB RAID device to install CentOS, then RAID5 the remaining 7 drives for all the data. I'l recreate the partitions above in the 1TB array, then use LVM to add the remaining 3.5TB into the LVs I need. I could also read up on array carving, that's new to me.
Thanks for all the help on this, I really thought I was doing something silly with the BIOS or some other setting. Didn't realize I would be running into limits of the OS.
Now, if anyone knows how to tune this thing for best write performance, that would be really cool. This server is part of a tapeless backup system using rsync. There's a good howto in the Linux Hacks book. We started from that, and it's just grown into a fully automated system that does hourly, daily and weekly backups. Plus, it sends it offsite to a colo location.... In case people were wondering why so much disk space...
Mark