Re: GPT Table broken on a Raid1

i used some disks one or two years ago of 1.5TB, when i boot the disk
for the first time the bios recognized it as a 1TB disk, i change some
bios parameters (removed from automatic) and i could put it to work
with 1.5TB could you check if it´s a bios problem? in my case the disk
appears as 1TB when it booted wrong, and after changing bios options
it goes nice with 1.5TB


2012/9/24 Chris Murphy [off-list ref]

On Sep 24, 2012, at 3:37 AM, John Robinson wrote:

quoted

On 23/09/2012 19:53, Chris Murphy wrote:
[...]

quoted

Upon creating a GPT on /dev/md/vol0, identical structures at identical byte offsets are created on /dev/sd[bc] and /dev/md/vol0.

The primary GPT header says the alternate header is at 0xffdfff.
The alternate GPT header is at 0xffdfff., or sector 16769023, right where it should be.

Regardless of whether the kernel sees the disk as Intel RAID or a bare disk, it finds the alternate GPT header, and doesn't complain about anything.

Yes, it does. It finds the alternate header just fine, according to the offset in the primary header, but warns that it's not at the end of the disc, which is where it expected to find it:

Not for me, is what I meant. Linux 3.5.3-1.fc17 does not complain about the alternate GPT header not being at the end of the disk. However, parted 3.0 does. And gdisk 0.8.5 does not.

Further, it seems increasingly clear as I'm reading the UEFI spec on GPT, that IMSM is incompatible with GPT. The GPT alternate header by spec is expected at the end of the disk, but then IMSM also demands to be in basically the exact same location. And yet Intel is shipping UEFI hardware, which require GPT disks, with IMSM on board that also requires metadata in the same location? How is this not a WTF moment?

I'm still wondering why parted reports Günther's disks have hybrid MBRs. That's weird, even if unrelated. And I wonder why his kernel complains about the GPTs not being at the end of the disk, but my kernel doesn't. Both are 3.5 kernels.


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Roberto Spadim
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