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Re: USB3 3TB HDD boot

From: Lennart Sorensen
Subject: Re: USB3 3TB HDD boot
Date: Mon, 4 Mar 2013 14:19:35 -0500
User-agent: Mutt/1.5.20 (2009-06-14)

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.  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.

Len Sorensen

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