From owner-freebsd-hackers@FreeBSD.ORG  Tue Jan 15 15:40:43 2013
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To: freebsd-hackers@freebsd.org,
 Karim Fodil-Lemelin <fodillemlinkarim@gmail.com>
Subject: Re: IBM blade server abysmal disk write performances
References: <50F563BE.7010609@gmail.com>
Date: Tue, 15 Jan 2013 09:40:23 -0600
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From: Mark Felder <feld@feld.me>
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On Tue, 15 Jan 2013 08:12:14 -0600, Karim Fodil-Lemelin  
<fodillemlinkarim@gmail.com> wrote:

> Hi,
>
> I'm struggling getting FreeBSD 9.1 properly work on an IBM blade server
> (HS22). Here is a dd output from Linux CentOS vs FreeBSD 9.1.
>

GNU dd is heavily buffered unless you tell it not to be. There really is  
no reason why you should want dd to be buffered by default. How can you  
trust that your attempt at writing raw data to a device actually completed  
if it's buffered?