From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from atl4mhob08.myregisteredsite.com ([209.17.115.46]:39983 "EHLO atl4mhob08.myregisteredsite.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750702AbaFVNnO (ORCPT ); Sun, 22 Jun 2014 09:43:14 -0400 Received: from mailpod1.hostingplatform.com (atl4obmail01pod1.mgt.hosting.qts.netsol.com [10.30.71.113]) by atl4mhob08.myregisteredsite.com (8.14.4/8.14.4) with ESMTP id s5MDhC4d007705 for ; Sun, 22 Jun 2014 09:43:12 -0400 Message-ID: <53A6DDAD.8070804@chinilu.com> Date: Sun, 22 Jun 2014 06:44:13 -0700 From: George Mitchell Reply-To: george@chinilu.com MIME-Version: 1.0 To: linux-btrfs@vger.kernel.org Subject: Re: btrfs on whole disk (no partitions) References: <2316027.LZEnVG8laK@xev> <6CA8020B-EB92-4A44-8AA5-3F69709F81F2@colorremedies.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 06/22/2014 12:49 AM, Imran Geriskovan wrote: >> The 64KB Btrfs bootloader pad is 8 sector aligned, so for 512e AF disks >> there's no problem formatting the whole drive. The alignment problem >> actually happens when partitioning it, using old partition tools that don't >> align on 8 sector boundaries. There are some such tools still floating >> around. > A 'somewhat' related question: > > So called Advanced Format drives has 4K physical sector size, > however they report 512B logical sector size. > > How does linux kernel access those drives? > 512B or 4K at a time? > > Imran > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > > This is a problem related to Western Digital drives. They lie in order to be compatible with older versions of Windows. Seagate AF drives report 4K, not 512B. Western Digital took this path in order to make the drives work with older Windows operating systems because Microsoft chose not to include support for AF drives until the last minute. As far as I know, btrfs defaults to 4K UNLESS you specify 512B when you create the file system and the kernel follows the filesystem, not the (in this case incorrect) info the drive reports, I could not find the documentation to confirm this, perhaps someone else can confirm it. Actually a 4K format will work just fine on a 512B drive AS LONG as the alignment is correct. The larger problem occurs when a 4K drive is formatted as 512B. But it is a real pain that the WD AF drives report as being conventional drives in order to not confuse Windows.