From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: util-linux-owner@vger.kernel.org Received: from ishtar.tlinx.org ([173.164.175.65]:54923 "EHLO Ishtar.hs.tlinx.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751153AbaJ1R3S (ORCPT ); Tue, 28 Oct 2014 13:29:18 -0400 Message-ID: <544FCE46.2090709@tlinx.org> Date: Tue, 28 Oct 2014 10:11:34 -0700 From: Linda Walsh MIME-Version: 1.0 To: dE CC: util-linux@vger.kernel.org Subject: Re: fdisk and 2048 sectors obsession. References: <544E923E.6050406@gmail.com> <544E97ED.7040406@earthlink.net> <544F0C88.1080807@gmail.com> <544F3B20.7090109@gmail.com> <544FA923.5080205@gmail.com> In-Reply-To: <544FA923.5080205@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Sender: util-linux-owner@vger.kernel.org List-ID: dE wrote: > 2048 is Windows behavior ported to utils-linux. It's pointless. Not if you move to any sort of RAID and want efficiency. Then 64k or 256k alignment is minimal. If you start at 1M, then layering other things on top, -- like default lvm blocks of 4M will still line up at 1M. Then when you layer RAID aware software like xfs on top of those, it can know how to do allocations and layout to allow optimal I/O on most RAID sizes. Anyone who uses RAID5 or RAID6 based underlying HW will appreciate file systems with full alignment to the underlying device stripes. Partial writes on those types of RAID's (or derivatives) requiring a complete read-modify-write cycle the size of the data stripe, so any underlying disk misalignment will really cause performance pain... But having all the disks start at 1M, you can usually move complete disk images around on devices and not get hurt by alignment issues.