From owner-freebsd-geom@FreeBSD.ORG Sat Feb 15 07:56:36 2014 Return-Path: Delivered-To: freebsd-geom@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 ESMTPS id 325B766A; Sat, 15 Feb 2014 07:56:36 +0000 (UTC) Received: from microbel.pvv.ntnu.no (microbel.pvv.ntnu.no [IPv6:2001:700:300:1900::1:2]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id DC8F01037; Sat, 15 Feb 2014 07:56:35 +0000 (UTC) Received: from 242.243.251.212.customer.cdi.no ([212.251.243.242] helo=nobby.localnet) by microbel.pvv.ntnu.no with esmtpsa (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.72) (envelope-from ) id 1WEa6v-0002WJ-Gw; Sat, 15 Feb 2014 08:56:31 +0100 From: Ulf Lilleengen To: freebsd-geom@freebsd.org Subject: Re: Allowing arbitrary MBR slice alignment Date: Sat, 15 Feb 2014 08:54:44 +0100 Message-ID: <7737397.rILaIf05sy@nobby> User-Agent: KMail/4.10.5 (FreeBSD/10.0-RELEASE; KDE/4.10.5; amd64; ; ) In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Spam-Score: -0.9 (/) X-Spam-Report: Status=No hits=-0.9 required=5.0 tests=ALL_TRUSTED, TVD_RCVD_IP version=3.3.1 Cc: Warren Block , ae@freebsd.org, marcel@freebsd.org, freebsd-geom@freebsd.org X-BeenThere: freebsd-geom@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: GEOM-specific discussions and implementations List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 15 Feb 2014 07:56:36 -0000 On Friday 14. February 2014 09.24.34 Warren Block wrote: > The Problem > > More and more disk devices have native 4K blocks. The ability to align > MBR slices to arbitrary values is consequently becoming more important. > Misaligned filesystems might read or write at less than half the speed > of aligned filesystems on the same disk. > > Microsoft recognized this problem, and at least since the release of > Vista in 2007, MBR-formatted disks created by Microsoft operating > systems have started the first or main filesystem slice at block 2048 > (1M). Despite the official standard for MBR alignment to CHS values, > this second non-CHS but 4K-aligned de facto standard has become > extremely common. *snip* > Suggested Solution > > gpart(8) should be allowed to override the CHS rounding with -a and -b > values when creating MBR slices. If CHS rounding occurs when the > options are not given, gpart(8) should give a warning that default > values were used to avoid surprising the user. > > The warning is really secondary. Primarily and pragmatically, gpart(8) > needs the ability to create MBR slices with arbitrary alignment so > FreeBSD can deal gracefully with modern storage hardware. > IMHO, 4k alignment should be default in freebsd as well, unless there are some actual disadvantages for the users. I think the majority of users would like good performance. But allowing to override it is a good start :) Ulf