[PLUG] 5TB RAID5, GTP & CentOS-5: what's going to bite me?

[JP Vossen <jp@jpsdomain.org>]

I posted about this a while ago, but I finally got CentOS-5.6 to boot 
from a 5TB hardware RAID5 device, using a GTP partition table and Grub2.

Normally, CentOS-5 will only boot from a device smaller than 2TiB due to 
MBR limits [1].  Using a GPT partition table fixes that, but Grub Legacy 
doesn't know about GPT; you either need a patch or Grub2.  Ubuntu 
switched to Grub2 in 9.10, by the way...

As an aside, one of the things I found out is that RHEL6 is *still* 
using Grub Legacy [2], though per the spec file change log it was 
patched for GTP support in 2007.  So, Grub1?  WTH?!?  And patched in 
2007?  So why not RHEL5 GTP support?!?  AAAARRRGGHHHHH!!!

I tried using that RHEL6 patched Grub1, but it had build-deps that 
CentOS-5 couldn't satisfy, so I went the other way and looked at Fedora 
and FC.  I ended up with FC10 because RHEL5/CentOS-5 are circa 2007 and 
FC10 was the oldest "FC" that had Grub2.  So I downloaded the FC10 Grub2 
SRPM and rebuilt it on a CentOS-5 machine after installing a few build 
dependencies, then:
1) Configured the hardware RAID5
2) Booted an Ubuntu 10.04 LiveCD to use gparted to do the GPT and partitions
3) Rsynced my CentOS-5 install from a similar server
4) Booted a CentOS-5.5 LiveCD (OS is 5.6, but the 5.5 LiveCD was handy)
6) Mounted and chrooted into the root on the RAID5
7) grub2-install /dev/sda2
8) Rebooted to the RAID5

It booted, and it seems like everything more-or-less works. 
fdisk/sfdisk complains they don't know about GTP and say to use gparted, 
otherwise I haven't found any problems. Yet.


What haven't I thought of that's going to bite me?

Thanks,
JP

[1] http://en.wikipedia.org/wiki/Master_boot_record
	"...the maximum size of a partition or the maximum start address (both 
in bytes) cannot exceed 2.19 TB"

[2] 
http://ftp.redhat.com/pub/redhat/linux/enterprise/6Server/en/os/SRPMS/grub-0.97-70.el6.src.rpm
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