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Old 07-04-2010, 04:18 AM
Mike Viau
Default FW: Debian support on newer 4K Advanced format drives (rather than 512 bytes)

On the link http://www.ibm.com/developerworks/linux/library/l-4kb-sector-disks/index.html


Tip: If you want to dual-boot between Linux and an
older operating system that
requires cylinder alignment, try aligning the starts of all your
partitions on multiples
of eight cylinders. This translates to 8-sector alignment for optimum
disk performance as well as cylinder alignment for the older operating


It sounds like the term cylinders is used synonymously with sectors. Will this always be the case??

> On Sat, 3 Jul 2010 15:09:57 -0500 <stan@hardwarefreak.com> wrote:
> Ron Johnson put forth on 7/3/2010 2:36 PM:
> >> This is unrelated. FS block size != sector size.
> >
> > It is when you use a 4KB drive!!!!
> Not according to man on Stable:
> mkfs.xfs [ -b block_size ] ... [ -s sector_size ] [ -L label ] [ -N ] device
> -b block_size_options
> This option specifies the fundamental block size of the filesystem. The
> valid block_size_options are: log=value or size=value and only one can be
> supplied. The block size is specified either as a base two logarithm value
> with log=, or in bytes with size=. The default value is 4096 bytes (4 KiB),
> the minimum is 512, and the maximum is 65536 (64 KiB). XFS on Linux currently
> only supports pagesize or smaller blocks.
> -s sector_size
> This option specifies the fundamental sector size of the filesystem. The
> sector_size is specified either as a value in bytes with size=value or as a
> base two logarithm value with log=value. The default sector_size is 512 bytes.
> The minimum value for sector size is 512; the maximum is 32768 (32 KiB). The
> sector_size must be a power of 2 size and cannot be made larger than the
> filesystem block size.
> --
> Stan

That seems like a very clean way to prepare a XFS file system that is aware of the 4096 byte sector size with the -s option. Its like away to override the 4096 byte sector size even if it gets read incorrectly as 512 by the /sys/block/sdX/queue/physical_block_size.


In theory, the Linux kernel should return information on the physical
sector size in the /sys/block/sdX/queue/physical_block_size pseudo-file
on the logical sector size in the
pseudo-file, where sdX is your device's node name (normally sda, sdb,
so on). In practice, however, the physical block size information is
spurious, at least for the first generation of Western Digital Advanced
Format drives. Unfortunately, this means that disk utilities cannot
properly detect the presence of such disks.



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