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From: John Baldwin <jhb@freebsd.org>
To: freebsd-hardware@freebsd.org
Subject: Re: What's the state of AF-4Kn support?
Date: Thu, 10 Oct 2013 16:57:22 -0400
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 (bigwig.baldwin.cx); Thu, 10 Oct 2013 17:03:13 -0400 (EDT)
Cc: Ravi Pokala <rp_freebsd@mac.com>, freebsd-hackers@freebsd.org,
 Jia-Shiun Li <jiashiun@gmail.com>
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On Monday, September 23, 2013 10:58:19 am Ravi Pokala wrote:
> -----Original Message-----
> From: Jia-Shiun Li <jiashiun@gmail.com>
> Date: Sunday, September 22, 2013 11:22 PM
> To: Ravi Pokala <rp_freebsd@mac.com>
> Cc: "freebsd-hardware@freebsd.org" <freebsd-hardware@freebsd.org>,
> <freebsd-hackers@freebsd.org>
> Subject: Re: What's the state of AF-4Kn support?
> 
> >On Wed, Sep 18, 2013 at 10:49 PM, Ravi Pokala <rp_freebsd@mac.com> wrote:
> >>
> >>...
> >
> >CC -hackers.
> >
> >Thanks for the clarification. Is there any 4Kn HDDs shopping now? I am
> >not aware of any.
> 
> Good question. I had the impression that some currently shipping drives
> were AF-4Kn, but spot-checking some of the drives listed in
> 
>     src/cam/ata/ata_da.c::ada_quirk_table[]
> 
> against their datasheets, suggests that they're AF-512e. So, their being
> flagged w/ ADA_Q_4K is "just" a performance optimization.
> 
> >BTW I believe UFS and ZFS have proper design for 4K-sectors, but FreeBSD
> >needs some ecosystem connections to get samples early to test,
> >incorporate supports and validate for it. Or we will need to wait until
> >it appears on market and someone got caught into some kind of bugs.
> 
> Yeah, based on my reading of the code, it looks like the ATACAM layer and
> higher (GEOM, filesystems) take the physical block size into account. That
> just leaves the bootstrap code. Now that I've taken a second look, it
> seems as though at least 'pmbr' only works in terms of 512 bytes. :-(

Yes, the BIOS calls have always only used 512 byte sectors.  There would
have to be an updated spec for those, and it would be a bit of a PITA to
use.  I suspect the "right" answer for this on x86 is UEFI.

-- 
John Baldwin