Date: Mon, 23 Sep 2013 11:38:44 -0500 From: Dan Nelson <dnelson@allantgroup.com> To: Jia-Shiun Li <jiashiun@gmail.com> Cc: Ravi Pokala <rp_freebsd@mac.com>, freebsd-hackers@freebsd.org, "freebsd-hardware@freebsd.org" <freebsd-hardware@freebsd.org> Subject: Re: What's the state of AF-4Kn support? Message-ID: <20130923163844.GE97298@dan.emsphone.com> In-Reply-To: <CAHNYxxNrMndF=s-s=YL4_7MNJ4ZENJ8YbVNzijOqo5XqZ2v2cw@mail.gmail.com> References: <CAHNYxxMZC7cw7TNBJMZewe3ABAS0S6Xaz%2BuDh2E_YbfP0fa2Pg@mail.gmail.com> <CE5F0282.F39EF%rpokala@mac.com> <CAHNYxxNrMndF=s-s=YL4_7MNJ4ZENJ8YbVNzijOqo5XqZ2v2cw@mail.gmail.com>
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In the last episode (Sep 23), Jia-Shiun Li said: > On Wed, Sep 18, 2013 at 10:49 PM, Ravi Pokala <rp_freebsd@mac.com> wrote: > > 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.html ]; > > 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. I don't think there are any yet, but some SATA->USB drive enclosures will present a 4Kn drive to the host if the physical drive is 512e. The Seagate Backup Plus does this at least. It lets you continue to use MBR-based partitioning and still access all of a 4TB disk. Unfortunately, since both GPT and MBR work off of block offsets, partitions created in one mode won't work in the other, so you can't just swap a disk in and out of the enclosure without (carefully) repartitioning. -- Dan Nelson dnelson@allantgroup.com
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