From owner-freebsd-hardware@FreeBSD.ORG  Wed Sep 18 10:38:08 2013
Return-Path: <owner-freebsd-hardware@FreeBSD.ORG>
Delivered-To: freebsd-hardware@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTP id 71C9537D
 for <freebsd-hardware@freebsd.org>; Wed, 18 Sep 2013 10:38:08 +0000 (UTC)
 (envelope-from jiashiun@gmail.com)
Received: from mail-vc0-x22f.google.com (mail-vc0-x22f.google.com
 [IPv6:2607:f8b0:400c:c03::22f])
 (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits))
 (No client certificate requested)
 by mx1.freebsd.org (Postfix) with ESMTPS id 3412D2FEC
 for <freebsd-hardware@freebsd.org>; Wed, 18 Sep 2013 10:38:08 +0000 (UTC)
Received: by mail-vc0-f175.google.com with SMTP id ia10so4955824vcb.20
 for <freebsd-hardware@freebsd.org>; Wed, 18 Sep 2013 03:38:07 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113;
 h=mime-version:in-reply-to:references:from:date:message-id:subject:to
 :cc:content-type;
 bh=anVqdQKYFbuLacMnh9LHRP00PyLA31JgjxlT1w7nkHg=;
 b=KKByYZJXSPW4BV4N56ynYWcH2/+dMWZ+kuumrbyniX4MfzyJagmx2/WyEGhQRj5MiT
 XzP7/JChH+koMIW+UIR3mCzZVvj9q8MaGdfZpWfGlOMVpfehRYRj8dsuMmRb3WsRvsV4
 4xdfPrIgsSLTwOBdHlDkLp+fY6DdQrFIVHlDVhKsSuPcfwXTy/+MgVlQMnJmv+9EWsty
 I1Nx85AkFSyiqAYuruZ3ZivfY2f7pXtsTWkHA9ivLi6CtqWgRBdW8Jj+kjXwkAyQys+d
 +JbK6wUrnEL3sNDTuDYJAIOW1vAHPu2bfmt0M/NAMzLv/uFsjAS9j38KQVEudfN2NaMW
 xOcg==
X-Received: by 10.220.237.208 with SMTP id kp16mr37052309vcb.4.1379500687315; 
 Wed, 18 Sep 2013 03:38:07 -0700 (PDT)
MIME-Version: 1.0
Received: by 10.58.225.34 with HTTP; Wed, 18 Sep 2013 03:37:37 -0700 (PDT)
In-Reply-To: <CE595AF7.F2BF7%rp_freebsd@mac.com>
References: <CE595AF7.F2BF7%rp_freebsd@mac.com>
From: Jia-Shiun Li <jiashiun@gmail.com>
Date: Wed, 18 Sep 2013 18:37:37 +0800
Message-ID: <CAHNYxxMZC7cw7TNBJMZewe3ABAS0S6Xaz+uDh2E_YbfP0fa2Pg@mail.gmail.com>
Subject: Re: What's the state of AF-4Kn support?
To: Ravi Pokala <rp_freebsd@mac.com>
Content-Type: text/plain; charset=UTF-8
Cc: "freebsd-hardware@freebsd.org" <freebsd-hardware@freebsd.org>
X-BeenThere: freebsd-hardware@freebsd.org
X-Mailman-Version: 2.1.14
Precedence: list
List-Id: General discussion of FreeBSD hardware <freebsd-hardware.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-hardware>, 
 <mailto:freebsd-hardware-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hardware>
List-Post: <mailto:freebsd-hardware@freebsd.org>
List-Help: <mailto:freebsd-hardware-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hardware>, 
 <mailto:freebsd-hardware-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 18 Sep 2013 10:38:08 -0000

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.