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

[Ravi Pokala]

-----Original Message-----
From: Jia-Shiun Li <jiashiun at gmail.com>
Date: Sunday, September 22, 2013 11:22 PM
To: Ravi Pokala <rp_freebsd at mac.com>
Cc: "freebsd-hardware at freebsd.org" <freebsd-hardware at freebsd.org>,
<freebsd-hackers at 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 at 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. :-(

WRT to getting samples, it may be possible to share some w/ appropriate
members of the community; who would those people be?

>Regards,
>Jia-Shiun.

Thanks,

rp