From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: Comment on ATA 4 KiB sector issues Date: Wed, 10 Mar 2010 14:46:38 +0900 Message-ID: <4B97323E.1040807@kernel.org> References: <4B95AEF6.8030906@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from hera.kernel.org ([140.211.167.34]:39066 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752551Ab0CJFqw (ORCPT ); Wed, 10 Mar 2010 00:46:52 -0500 In-Reply-To: Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Tomasz Palac Cc: linux-ide@vger.kernel.org Hello, On 03/09/2010 06:22 PM, Tomasz Palac wrote: >> Using custom geometry is a good way to trick a partitioner which >> partitions based on CHS alignment to align to larger units but it >> isn't meaningful outside of that. If CHS dosen't follow 255*63, a lot >> of code (firmware, BIOS, boot loader, OS...) will just assume CHS is >> incorrect. > > As of firmware, Large Disk Howto states that a lot of SCSI host > adapters are using 64/32 geometry (at least for disks smaller than 8 > GiB). If BIOS supports EDD (INT13h Extensions), then disk geometry > is irrelevant. Yes, the geometry is basically arbitrary values which can be queried using a BIOS call and the reason why SCSI hosts can choose them is they implement BIOS extensions themselves. > If not, then geometry can be read from partition table. >>From where? > The only problem with 64/32 geometry is 1 GiB (as opposed to 8 GiB) > limit for boot partition (without using EDD). The same applies to > boot loaders. Modern OSes don't use CHS. For modern OSes, geometry doesn't matter at all. Older ones are the ones having problems (I've been corrected: XP seems okay while 2000 depends on CHS). Thanks. -- tejun