Getting Over the 2.2TB Bootable Storage Volume Limit in RHEL 6

Getting Over the 2.2TB Bootable Storage Volume Limit in RHEL 6

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Getting Over the 2.2TB Bootable Storage Volume Limit in RHEL 6

Posted on behalf of Ashokan Vellimalai – Linux Engineering

Systems based on conventional BIOS use DOS MBR (Master Boot Record) partitioning scheme which imposes a limit of 2.2TB for a maximum disk or partition size on any operating system.

Dell PowerEdge Servers have offered storage volumes greater than 2.2 TB for a while. While booting disks/volumes larger than 2.2TB is possible, a few requirements must be satisfied:

Here is a brief comparison of MBR and GPT partitioning schemes:

Functionality

MBR Disk

GPT disk

Legacy OS like MS DOS, MS Windows

Yes No

Greater than 2.2TB (Tera Byte)

No Yes

Data disk in x86_64 and x86 version of OS

Yes Yes

Boot disk in x86_64 version of OS

Yes Yes

Boot disk in x86 version of OS

Yes No

More than 4 primary partition

No Yes
(up to 128 Partitions)

BIOS Mode Booting

Yes

Implementation Specific

UEFI Mode Booting

No Yes

 

Now, we have servers which support partition sizes greater than 2.2 TB through UEFI/GPT. How do we use it? What changes are needed in the Operating System, Boot loader and file systems to enable support for these volumes?

Red Hat’s recently announced RHEL 6 fully supports UEFI/GPT based systems. Dell has ensured that RHEL 6’s UEFI/GPT components were thoroughly validated and known bugs fixed for a seamless deployment.

Here is how you can setup RHEL6 on bootable storage volumes/disks greater than 2.2TB:

1. Enable UEFI boot mode in BIOS boot settings and have your RHEL 6 DVD handy, or you can install the OS through UEFI PXE boot (but that would require setting up or modifying existing PXE server setup to include UEFI support).

2. Once UEFI boot manager initializes, change the UEFI boot sequence to boot from DVD image and follow on-screen installation steps to go to partition layout screen.

3. The default automatic partitioning scheme will create /boot/efi, /boot, and LVM volume groups by default and it sets the disk label to GPT. If you want to explore more on custom partitions, choose custom partition layout, and create /boot/efi  (50-256 MB recommended), and /boot and / partition with size greater than 2.2 TB and proceed with the installation.

The detailed steps for UEFI based RHEL6 installation can be found in the RHEL 6 Installation Guide and in the RHEL6 Installation and Important Information on Dell PowerEdge Servers.

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