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piotr5
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PostPosted: Fri Sep 05, 2014 12:22 pm    Post subject: what does hda=stroke do? Reply with quote

on the minimal install disc I booted with this option. then I started fdisk and the dos-table still ends at 4294967294 with 2TiB. is this an obsolete option? is this supposed to turn on GPT support in the kernel or something? is it really required for GPT?
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eccerr0r
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PostPosted: Fri Sep 05, 2014 1:07 pm    Post subject: Reply with quote

It's for old BIOS that doesn't know how to report the correct geometry for the hard drive. Modern firmware should not need this option.
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py-ro
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PostPosted: Fri Sep 05, 2014 1:50 pm    Post subject: Reply with quote

And yes MBR on Harddisk >2TB is a bad Idea.

You can use MBR to address almost 4TB.

The start of a Partition is the sector count from the beginning of the disc with a max of 2TB, the length has the same limit, so you can in theory make partition at 2TB -1 Sector, with a length of 2TB and use up to 4TB. But it is a bad bad idea and strange behaviour of different software will happen.

So on disks >2TB use GPT.

Bye
Py
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NeddySeagoon
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PostPosted: Fri Sep 05, 2014 8:11 pm    Post subject: Reply with quote

piotr5,

In days of old big HDD used to lie about their actual capacity is the BIOS would not boot from them.
Its happened several times in the history of the PC. Most recently at 33G and 137G. hda=stroke regains the lost space due to the HDD reporting that it was smaller than its actual capacity to keep the BIOS happy.

I don't share py-ros optimism that you can use MBR to address almost 4TB. What he says about the data structures on the partition table is correct but collect operation would depend on >32 bit arithmetic being used.
It won't work on a 32 bit CPU and if it works on a 64 bit CPU its pure luck.

The sector counting in MSDOS partition tables uses 32 bit values, which gets you 2^32 addressable sectors. Then its game over.
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piotr5
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PostPosted: Fri Sep 05, 2014 9:38 pm    Post subject: Reply with quote

thanks. seems my bios-hdd-combination doesn't have that bug, doesn't require this kernel-option.

as "logical volume manager" isn't of any help either (seems it would reside at the beginning of disc and prevent MBR too) I'll have to test my idea of changing protective partition into a windows-partition. if that doesn't work, I'll look into increasing the sector-size. (anybody knows where I could find info on that? is it an option I could set in the bios? fdisk doesn't seem to show that.) what I want is to dual-boot between windows and linux on a 3tb disk with pre-gpt bios and 32bit cpu.

ideally I should cover part of the hdd with old partition and give linux control over the rest. guess I'd need to alter sourcecode of lvm to make a physical volume at the position of my disc where I want it to go. would definitely work much better than creating a big partition at the end of all other ones. (well, actually it's the very same idea, except the lvm device would be stored in 2 places, the hdd itself with large offset for the data, and some spare partition for the lvm headers. i.e. adding the volume to a group would require specifying both devices instead of just one. I'm not sure the kernel could handle that.) I admit, my problem is a bit obscure, most people use 64bit processors and windows-xp or better. I can understand nobody is working on that...
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NeddySeagoon
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PostPosted: Sat Sep 06, 2014 8:48 am    Post subject: Reply with quote

piotr5,

You cannot install a Windows boot loader on a disk partitioned the way you describe.
Hmm maybe if you hack on the Windows boot loader so you can move it somewhere else.
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Computer users fall into two groups:-
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