File system blocks alignment

Alexander Motin mav at
Fri Dec 25 11:27:43 UTC 2009

Thomas Backman wrote:
> On Dec 25, 2009, at 11:58 AM, Alexander Motin wrote:
|>> Recently WD released first series of ATA disks with increased physical
>> sector size. It makes writes not matching with 4K blocks inefficient
>> there.
> They don't expose this to the OS, though (not by default, anyway), but chop it up into 8 512-byte sectors for compatibility reasons.
> Just thought I'd point that out - I'm not even sure if you can get them to *not* do the compatibility thing and expose 4k-sized sectors.

Latest ATA-8 specification allows drive to report both logical (512B)
and physical (4KB) sector sizes. ada driver able to fetch and report
that info to GEOM. If these drives not reporting it yet (are you really
sure?), it is only question of their firmware.

Alexander Motin

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