Date: Wed, 18 Sep 2013 18:37:37 +0800 From: Jia-Shiun Li <jiashiun@gmail.com> To: Ravi Pokala <rp_freebsd@mac.com> Cc: "freebsd-hardware@freebsd.org" <freebsd-hardware@freebsd.org> Subject: Re: What's the state of AF-4Kn support? Message-ID: <CAHNYxxMZC7cw7TNBJMZewe3ABAS0S6Xaz%2BuDh2E_YbfP0fa2Pg@mail.gmail.com> In-Reply-To: <CE595AF7.F2BF7%rp_freebsd@mac.com> References: <CE595AF7.F2BF7%rp_freebsd@mac.com>
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On Sat, Sep 14, 2013 at 3:14 PM, Ravi Pokala <rp_freebsd@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.
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