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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