File system blocks alignment

Alexander Motin mav at
Mon Dec 28 12:30:32 UTC 2009

Miroslav Lachman wrote:
> Alexander Motin wrote:
>> 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.
> There is an article about 4k sectors
> It is completely hidden to OS in first versions.

Thanks for the link, but all I see there is "but at this point there’s
no such tool". IMHO it doesn't meet it is not reported.

We just need somebody with that drive to run on it `camcontrol identify`
from the fresh system and report what he sees.

Alexander Motin

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