[vbox-dev] Booting from Big Disks: What is LBA64 ? And does it require EFI ?

Frank Mehnert frank.mehnert at oracle.com
Fri Dec 18 21:48:34 GMT 2015


On Friday 18 December 2015 23:40:38 Alexey Eromenko wrote:
> >From changelog
> "BIOS: added LBA64 support for being able to boot from huge hard disks
> (bug #7415)"
> I don't understand it.
> 1. Is it possible to boot hard disks > 2 TB with BIOS? or does it
>    require EFI ?

In VirtualBox term: BIOS = BIOS; EFI = EFI. Therefore this change
allows the BIOS to boot from huge hard disks. EFI is not affected.

> 2. Is it possible to boot hard disks > 2 TB with MBR ? or does it
>    require GPT ?

That depends on the operating system. As long as the OS kernel
didn't take over, the OS boot loader uses the BIOS to access
the hard disk. To be able to read/write sectors beyond the 2TB
limit, LBA64 is required.

> 3. Where is LBA64 standard defined ? Is there something like
>    open IETF RFC specification for it ?

I don't know but I'm sure your favourite Internet search portal
will help :-)

> I always thought that both EFI + GPT are mandatory for big disks, so
> MBR and calssic BIOS won't work, but this changelog raises questions.

As I said above, this change is about BIOS, not about EFI.

Kind regards,

Dr.-Ing. Frank Mehnert | Software Development Director, VirtualBox
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