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Re: USB3 3TB HDD boot

From: Vladimir 'φ-coder/phcoder' Serbinenko
Subject: Re: USB3 3TB HDD boot
Date: Mon, 04 Mar 2013 20:33:51 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.12) Gecko/20130116 Icedove/10.0.12

On 04.03.2013 20:19, Lennart Sorensen wrote:

> On Mon, Mar 04, 2013 at 08:27:41PM +0400, Bob Lemar wrote:
>> Thank you for your replies.
>> Yes, it is definitely BIOS problems as it doesn't allow to boot from
>> external drive directly (via BIOS boot order settings). It doesn't
>> show this drive at <F10> boot menu even after soft reboot. So BIOS
>> doesn't provide access to GRUB like to any other drives or USB
>> flashes.
>> And I suppose to think that it is not a bug, it is a feature. And
>> feature of external drive, not a BIOS. Vendors of spinning external
>> drive try to limit "uptime" of theirs HDD. External HDD could start as
>> soon as USB is powered but do not want to do it. It only starts when
>> OS tell it to start up (this commands are magic for me).
>> Facts:
>> - External drive is logically 4K (not a 512e thing). It is not a problem yet.
>> - USB 3 is not a problem yet. The drive doesn't work with USB 2 just
>> the same way. So it is not "nativeness" BIOS-USB hub communication
>> problem.
>> - BIOS behavior is correct (it power up USB);
>> - external drive behavior is correct (it is powered but starts only on
>> demand and it is sleeping in many cases including PC start);
>> - GRUB behavior is correct (it boots from drives that BIOS told him
>> about; only OS can detect this device as mass storage because it was
>> designed that way).
>> - Ales, you were absolutely right with floppy for booting CD trick
>> example. While MB, HDD firmwares and bootloader have predictable and
>> correct behavior some users would like to have bootloader feature
>> (GRUB command) that wake up external HDDs and re-detect drives.
>> Resolution:
>> - Boot USB thumb and use kexec to boot external HDD.
>> I did: (1) clone linux to external drive; (2) correct fstab at
>> external; (3) boot into internal drive OS; (4) mount external HDD
>> which became visible; (5) kexec images and boot external drive. // I
>> am not sure that only external drive files were used at second boot --
>> need to do clear experiment with minimal os at internal device or
>> thumb flash. kboot and petitboot are possible solve this problem.
>> - It is good point to create feature request at BugTracker. I wish
>> GRUB has command to power up external USB HDD and do manual redetect.
>> But I don't know what is happening technically when OS do it. I guess
>> I should find out it to be more specific while filling bug.
> The fact it is 3TB would mean it uses GPT, not old style DOS partition
> table.

Not necessarily. 3T drives often use msdos, just with 4K sectors which
increases the range of msdos to 16T.

>  Maybe the BIOS doesn't support booting from a GPT partitioned
> drive.  If it had a hybrid partition table, then it might work assuming
> other things are not also causing problems.
> After all some bioses only list a drive as bootable if they see a
> partition marked bootable in a dos style partition table.

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