Re: USB3 3TB HDD boot

[Andrey Borzenkov]

В Thu, 14 Mar 2013 20:18:46 -0600
Chris Murphy <address@hidden> пишет:

> 
> On Mar 5, 2013, at 12:22 AM, Vladimir 'φ-coder/phcoder' Serbinenko 
> <address@hidden> wrote:
> 
> > On 05.03.2013 00:16, Chris Murphy wrote:
> > 
> >> 
> >> On Mar 4, 2013, at 12:43 PM, "Lennart Sorensen" <address@hidden> wrote:
> >> 
> >>> On Mon, Mar 04, 2013 at 08:33:51PM +0100, Vladimir 'φ-coder/phcoder' 
> >>> Serbinenko wrote:
> >>>> Not necessarily. 3T drives often use msdos, just with 4K sectors which
> >>>> increases the range of msdos to 16T.
> >>> 
> >>> Hmm, I suppose that would work.  I have never seen one that did that yet,
> >>> but I don't have that many 3TB drives either.
> >> 
> >> I wonder what the BIOS does when it "asks" the drive for LBA 0, and 
> >> receives 4096 bytes instead of 512 bytes.
> > 
> > It doesn't get that far. Most likely it bails out after reading SCSI
> > descriptor.
> 
> I have anecdotal evidence these drives are now in the wild. Mac user with a 
> new 3TB Seagate USB 3 external drive:
> Device / Media Name:      Seagate Backup+ Desk Media
> 
> This is not very descriptive. But when I ask the user to display the GPT with 
> gdisk, there's normal output, except for this line:
> Logical sector size: 4096 bytes
> 
> Next, when I have him report the result from:
> sudo dd if=/dev/disk3 count=2 2>/dev/null | hexdump -C
> 
> The 1st 512 bytes reported is the PMBR, but the 2nd 512 bytes is garbage, not 
> the GPT header as expected.
> 

It is possible that you need to read in physical sector size; what if
you try bs=4k?

> When this drive is connected to the computer and he tries to boot Windows, 
> the system hangs at a black screen. That's kinda interesting/concerning, if 
> even CSM-BIOS implementations on recent EFI firmware can have problems with 
> such drives.
> 
> 
> Chris Murphy
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