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I need a new HDD and plan on getting a 3TB one to fit all my stuff, ubuntu 12.04 install included.

So far I only have a 5yr old Asus p5qse but sooner rather than later I should have a new system with a new MB so I imagine UEFI as well.

My questions are :
Will the full 3TB be usable on my old MB?
And on a new MB?
Am I right to ask these questions, is it a BIOS problem? Or are these matters only relative to windows OSs and I should be fine no matter what?

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up vote 4 down vote accepted

Theoretically, you can format your 3TB disk to work with your old motherboard with BIOS via partitioning it with a GPT partition table rather than MSDOS. However, it's not totally foolproof. Some BIOSes attempt to validate partition tables when they should not and that can cause problems because of the "protective MBR" that a GPT-partitioned disk uses.

Do note that not all Linux disk tools work with GPT-partitioned disks. You would need to use gdisk rather than fdisk for example. The graphical Gparted and command line parted should have no problems with this.

So, really, there's no definite answer to this. However, all UEFI motherboards should be exempt from this problem.

If you're going to be dual-booting, you need to be sure that your new Windows OS has support for GPT partition tables (see EDIT 1). Windows will only install to a GPT if a) the OS supports booting from GPT (see below table), and b) you are using a UEFI firmware, so dual-booting using a pure GPT disk not supported -- of course you could always make a hybrid MBR.

EDIT 1: GPT features of Windows versions are kind of mixed.

Windows 95/98/2000/NT 4: Lol! Not a chance.
Windows XP 32-bit: No support
Windows XP 64-bit: Data disks only (no boot capability)
Windows Server 2003 SP1+: Data disks, booting only on 64-bit IA-32/Itanium systems.
Windows Vista/7/Server 2008: Data disks, booting only available on UEFI-based systems

Source: MSDN

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For my first question, the "it's complicated" answer is good enough for me as I lack the knowledge to understand a more developed one. And actually if I have a new system, my boot will probably be an SSD anyway so I guess you advised against me getting one :D and I thank you for saving me the trouble... – sinekonata May 18 '13 at 22:03
Well, I woudln't say that's a definite "no". BIOSes with the problem I mentioned are few and far between. I was just pointing out that it was a possibility, albeit a rare one. – Chuck R May 18 '13 at 22:30
One way to test it is to use a LiveCD/USB and temporarily wreck your MBR (after backing it up of course) and see if your BIOS complains about it. If you'd like I can update my answer with instructions on how to do that. – Chuck R May 18 '13 at 22:32
Also! This 2.2TB limit of the BIOS only applies to hard drives with 512-byte sectors. What is the model of the HDD you're looking at? – Chuck R May 18 '13 at 22:34
Windows cannot boot from a GPT disk on a BIOS-based computer, so if dual-booting with Windows is required, you should either use a sub-2TiB disk for booting Windows or upgrade the motherboard now. (Using DUET is another possibility, albeit one for experts.) Windows is fine with GPT on non-boot disks, though. – Rod Smith May 18 '13 at 22:45

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