From owner-freebsd-fs@FreeBSD.ORG Tue Jan 6 00:12:21 2009 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C2DEA106567A for ; Tue, 6 Jan 2009 00:12:21 +0000 (UTC) (envelope-from andrew@modulus.org) Received: from email.octopus.com.au (email.octopus.com.au [122.100.2.232]) by mx1.freebsd.org (Postfix) with ESMTP id 827338FC0C for ; Tue, 6 Jan 2009 00:12:21 +0000 (UTC) (envelope-from andrew@modulus.org) Received: by email.octopus.com.au (Postfix, from userid 1002) id 98A5517D9C; Tue, 6 Jan 2009 11:12:19 +1100 (EST) X-Spam-Checker-Version: SpamAssassin 3.2.3 (2007-08-08) on email.octopus.com.au X-Spam-Level: X-Spam-Status: No, score=-1.0 required=10.0 tests=ALL_TRUSTED, SUBJECT_FUZZY_TION autolearn=no version=3.2.3 Received: from [10.1.50.60] (ppp121-44-0-132.lns10.syd7.internode.on.net [121.44.0.132]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: admin@email.octopus.com.au) by email.octopus.com.au (Postfix) with ESMTP id 8AAC617231; Tue, 6 Jan 2009 11:12:15 +1100 (EST) Message-ID: <4962A1D6.4040508@modulus.org> Date: Tue, 06 Jan 2009 11:12:06 +1100 From: Andrew Snow User-Agent: Thunderbird 2.0.0.14 (X11/20080523) MIME-Version: 1.0 To: Koen Smits References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: freebsd-fs@freebsd.org Subject: Re: FreeBSD, SSD's and partition alignment X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 06 Jan 2009 00:12:22 -0000 > I'd like to discuss this subject a bit if anyone's interested. > - partition alignment seems to be a real problem with some of today's flash > and RAID media. I think people need to know one could easily increase > performance (and media wear!) as no one knows this problem exists. Thanks for your interesting post! In my humble opinion, FreeBSD should not worry about this problem for the following reasons: 1. Performance for random write I/O still sucks even when the sector boundary is correct. Doing something like untarring src or ports causes many small write I/Os, and it is simply a shortcoming of early generation flash controller technology that they erase and rewrite in large blocks. 2. This problem will go away when flash controller technology improves. Intel SSDs have already demonstrated they can have great performance *and* a small erase block size, mitigating the issue completely. This technology will trickle down to the cheaper flash SSDs over time. - Andrew