Non-UEFI limited to 2TB disk?

Tom H tomh0665 at gmail.com
Sat Feb 27 09:35:52 UTC 2016


On Sat, Feb 27, 2016 at 7:01 AM, Ralf Mardorf <silver.bullet at zoho.com> wrote:
> On Fri, 26 Feb 2016 22:07:31 -0500, Rashkae wrote:
>>
>> BIOS and MBR are both limited to max size of 2.19 TB.
>
> "[snip]
> The organization of the partition table in the MBR limits the maximum
> addressable storage space of a 512-sector disk to 3.99 TiB (232 × 512
> +232 × 512 bytes).[2] Therefore, the MBR-based partitioning scheme is
> in the process of being superseded by the GUID Partition Table (GPT)
> scheme in new computers. A GPT can coexist with an MBR in order to
> provide some limited form of backward compatibility for older systems.
> [snip]
> Since partitioning information is stored in the MBR partition table
> using a beginning block address and a length, it may in theory be
> possible to define partitions in such a way that the allocated space
> for a disk with 512-byte sectors gives a total size approaching 4 TiB,
> if all but one partition are located below the 2 TiB limit and the last
> one is assigned as starting at or close to block 232−1 and specify the
> size as up to 232−1, thereby defining a partition which requires 33
> rather than 32 bits for the sector address to be accessed. However, in
> practice, only certain LBA-48 enabled operating systems, including
> GNU/Linux, FreeBSD and Windows 7[20] that use 64-bit sector addresses
> internally actually support this.
> [snip]" - https://en.wikipedia.org/wiki/Master_boot_record

4TiB?!

The article [A] that's referenced by the "[2]" right after "2^32*512 +
2^32*512" doesn't mention 4GiB and it later says "Therefore, the
maximum disk size supported on disks using 512-byte sectors (whether
real or emulated) by the MBR partitioning scheme (without using
non-standard methods) is limited to 2 TiB."

"non-standard methods"?

[A] https://support.microsoft.com/en-us/kb/2581408




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