What's the state of AF-4Kn support?

[Jia-Shiun Li]

On Sat, Sep 14, 2013 at 3:14 PM, Ravi Pokala <rp_freebsd at mac.com> wrote:
> What does 4Kn support look like in -HEAD? I know UFS's defaults (32KB
> blocks / 4KB fragments) are 4Kn-friendly, and that `gpart' handles
> alignment properly. What about direct drive I/O (i.e. do the device
> drivers do the proper read/modify/write stuff if you try to write a
> partial block)? What about the bootstrap code; I've looked at pmbr.s and
> gptboot.c, and it's not clear if they DTRT in the face of 4Kn drives.

RMW is done in HDD firmware. The HDDs still do 512b-sector I/Os,
only giving additional hint that physically it is 4K and if aligned
performance would be better. Functionally speaking there is
no difference from not-so-advanced-format (if cost-down is an
advance) HDDs.

Jia-Shiun.