New UEFI guide on the wiki

[Chris Murphy]

On Feb 6, 2014, at 12:39 AM, Dariusz J. Garbowski <thuforuk at yahoo.co.uk> wrote:

> On 05/02/14 05:46 PM, Przemek Klosowski wrote:
>> On 02/04/2014 06:18 PM, Chris Murphy wrote:
>>> And then we can definitely justify making them bigger. 550MB, or even 1GB. It's neutral to plus
>>> for performance for either HDDs or SSDs (faux short stroked in the former, and overprovisioned for
>>> the latter). Does anyone know why the convention is to create the ESP as the first partition?
>> At times in the past there was a race between BIOS support for large disks and hard disk size, and
>> BIOS boot code could not reach the far sectors of the disk. This even leaked into Linux sometimes,

Right but BIOS only ever expected to have to read LBA 0, so it stands to reason someone's not testing whether it can jump beyond LBA 28-bit addressing if it's an ancient BIOS implementation; or beyond the MBR 32-bit address limit.

But since the UEFI spec is predicated on LBA 48-bit addressing, I think my diplomatic language would be "WTF vendor" if UEFI firmware face planted on an ESP at the end of a 5TB drive. I should test it. 

Oh hey, it works with whatever UEFI VirtualBox uses. This is the layout. Firmware finds shim.efi way out well beyond 3TB, and GRUB is finding its grub.cfg way out there as well and boots the system fine.

Disk /dev/sda: 10240000000 sectors, 4.8 TiB
[…]
Number  Start (sector)    End (sector)  Size       Code  Name
   1     10238871552     10239999966   551.0 MiB   EF00  EFI System
   2            2048         1026047   500.0 MiB   0700  
   3         1026048     10238871551   4.8 TiB     0700  




> It still happens: I just had a case of this on Dell R620 (Ivy Bridge Xeon) with over 3TB disk space and RHEL 6.5... Grub couldn't reach it's files to boot OS.

RHEL 6.5 uses ancient GRUB 0.97 so the problem could be with the boot loader, or the firmware.

However, without having this computer physical present, how can you tell it uses UEFI and not BIOS? I certainly can't. Dell's spec sheet for it says in part "From bezel to BIOS to packaging" which seems like just a tagline, not a spec per se. But then the support page explicitly refers to it as BIOS:

Dell Server BIOS PowerEdge R620 Version 2.1.3
http://www.dell.com/support/drivers/us/en/04/DriverDetails/Product/poweredge-r620?driverId=T2RVC&osCode=WS8R2&fileId=3329675946&languageCode=en&categoryId=BI

In general, finding out whether a system's firmware is BIOS or UEFI is not easy. Either they don't say, as if it isn't a selling point, yet telling me it uses the, e.g. Intel C600 chipset isn't too obscure. HP pretty much universally refers to the UEFI firmware updates as BIOS updates. Idiotic.


Chris Murphy