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Re: Support for 4KB sectors size disk ? wrote:

> Is this still a problem with GPT (or what is the "new" windows
> partitioning called)?

I think GPT just handles >2^32 logical block address
(i.e. 2TB disk with 512bytes/sector disk).

MBR (and probably GPT) has LBA numbers in it, but
I wonder what number should be used for unit of LBA
(512bytes constant or actual hardware sector size)
and whether PC BIOS can recognize actual hardware sector size
or not.

On i386 and amd64, there is another problem around bootloader.

Currently FFS has only 8KB free space for bootloader.
On x86, the first sector contains PBR that loads
bootxx_ffsvN stored in the following sectors:

sector 0:    PBR (pbr.S in src/sys/arch/i386/stand/bootxx/)
sector 1:    NetBSD disklabel
sector 2-15: primary boot (bootxx.S, boot1.c, and fs specific code)

But on 4KB/sector disk, sector 1 is at 4KB (that should have disklabel?),
and sector 2 is at 8KB where FFS superblock should be stored.

We have to consider where disklabel and bootloader should be stored
and what other OSes do on !512bytes/sector disks.

Probably we should abandon disklabel and support such disks
only with GPT and dk(4), but we have to still consider where
bootloader should be stored (at offset 512 of sector 0, or at sector 1)
and how BIOS can load it.
Izumi Tsutsui

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