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

["Gavin W. Burris" <bug@sas.upenn.edu>]

There is no need for the live CDs.  You can do this with a standard
install CD/DVD.  The trick is, prior to installing the OS, create a
~100GB virtual disk with the raid bios, carving up the remaining disk
space for your data virtual disks as you see fit.

If the installer then complains about the GPT partitioning, switch to
the terminal screen and overwrite the beginning of the block device with
random data:
# dd if=/dev/urandom of=/dev/sda bs=512 count=64

Cheers.

On 06/16/2011 03:15 AM, JP Vossen wrote:
> 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
> 
> ----------------------------|:::======|-------------------------------
> JP Vossen, CISSP            |:::======|      http://bashcookbook.com/
> My Account, My Opinions     |=========|      http://www.jpsdomain.org/
> ----------------------------|=========|-------------------------------
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-- 
Gavin W. Burris
Senior Systems Programmer
Information Security and Unix Systems
School of Arts and Sciences
University of Pennsylvania
___________________________________________________________________________
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