How to create GPT disk label in RHEL or CentOS....???error "sda Must have a GPT disk label"

GPT(GUID Partition Table)
MBR and GPT are two different ways of storing the partitioning information. In RHEL6 the default way of partitioning a harddisk is to use a MS-DOS disk label.This type of partitioning a hard disk is an old method.Unfortunately this way of partitioning does have some problems that is MBR works with disks up to 2TB, But it can't handle disks more than 2TB.

NOTE:- RHEL 6.3 or later the installer will automatically use GPT partitioning for disks larger than 2TB in size.

Have you ever seen this error "sda Must have a GPT disk label" while installing RHEL (or) CentOS

 
Disable UEFI Mode in your machine BIOS setup 

[OR] 

Another way you can use PARTED Utility to resolve this issue:-

parted is a command which is used for disk partitioning and partition resizing program.

First PRESS CTRL+ALT+F2 to go to terminal for running parted utility from GUI

# parted
(parted) print /dev/sda

(parted) select /dev/sda

(parted) mklabel gpt

(parted) yes

(parted) print /dev/sda

(parted) quit

 Finally PRESS CTRL+ALT+F1 for return back to GUI mode.