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

[rozhuk.im at gmail.com]

# install
gpart create -s GPT ada1
gpart show
gpart add -i 1 -t freebsd-boot -b 40 -s 512 ada1
gpart add -i 2 -t freebsd-ufs -b 552 -s ..... ada1
gpart bootcode -b /boot/pmbr ada1
gpart bootcode -p /boot/gptboot -i 1 ada1


# for data
gpart create -s GPT ada1
gpart show
gpart add -i 1 -t freebsd-ufs -b 40 -s ..... ada1


> -----Original Message-----
> From: owner-freebsd-hackers at freebsd.org [mailto:owner-freebsd-
> hackers at freebsd.org] On Behalf Of Jia-Shiun Li
> Sent: Monday, September 23, 2013 10:23 AM
> To: Ravi Pokala
> Cc: freebsd-hackers at freebsd.org; freebsd-hardware 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:
> >
> > What you describe is the 'AF-512e' format - 4KB physical sectors
> > *emulating* 512B logical sectors. See [
> > https://en.wikipedia.org/wiki/Advanced_Format#Advanced_Format_512e ;
> > http://www.idema.org/?page_id=2153 ]. With AF-512e, yes, the HDD
> > firmware does the read/modify/write for I/Os smaller than the
> physical sector size.
> > It is intended to be a low-cost/transitional format, allowing the HDD
> > vendors to get the advantages of 4KB physical sectors (better error
> > detection/correction algorithms, better areal density => lower cost)
> > w/o breaking compatibility with decades of firmware and software that
> > expect 512B logical sectors.
> >
> > What I'm asking about is AF-4kn - 4KB *logical* as well as physical
> > sectors. All the enterprise HDD vendors have told us is that AF-4Kn
> > drives expect data IO to be 4KB, and will reject smaller transfers.
> > (*metadata* IO - SMART, IDENTIFY_DEVICE, READ_LOG/WRITE_LOG, etc -
> > will remain 512B.)
> >
> > Doing some more digging, I found this post from ivoras which I missed
> > the first time around [
> > http://ivoras.net/blog/tree/2011-01-01.freebsd-on-4k-sector-
> drives.htm
> > l ]; that tends to support my initial assessment - filesystem stuff
> > should Just Work[tm] - plus adds the detail that direct drive I/O
> (the
> > example he gives is trying to `dd' 10 bytes) will be rejected because
> > it is smaller than the raw-device access granularity. I've also
> looked
> > at 'ata_da.c' and see that adaregister() looks at both quirks and
> > IDENTIFY_DEVICE data to determine the logical block size.
> >
> > So, that leaves the bootstrap code as the remaining question-mark.
> > Does anyone what AF-4Kn support looks like there?
> >
> 
> CC -hackers.
> 
> Thanks for the clarification. Is there any 4Kn HDDs shopping now? I am
> not aware of any.
> 
> 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.
> 
> Regards,
> Jia-Shiun.
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