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Re: USB3 3TB HDD boot

From: Chris Murphy
Subject: Re: USB3 3TB HDD boot
Date: Thu, 14 Mar 2013 20:56:18 -0600

On Mar 14, 2013, at 8:38 PM, Andrey Borzenkov <address@hidden> wrote:
>> 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?

Right, for a 4Kn drive, to read LBA 1 and get the GPT header I'd need:

sudo dd if=/dev/disk3 skip=8 count=1 2>/dev/null | hexdump -C

Chris Murphy

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