From: Greg Freemyer Subject: Re: defrag deployment status (was Re: [PATCH] ext4: allow defrag (EXT4_IOC_MOVE_EXT) in 32bit compat mode) Date: Mon, 8 Mar 2010 11:31:49 -0500 Message-ID: <87f94c371003080831n4d310e10i2b9badf4290f1ede@mail.gmail.com> References: <201003072132.10579.borntraeger@de.ibm.com> <4B94367E.9080506@garzik.org> <201003080853.42978.borntraeger@de.ibm.com> <4B9518DA.8010201@davidnewall.com> <4B952437.8020607@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: David Newall , Christian Borntraeger , Jeff Garzik , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, Akira Fujita To: jim owens Return-path: Received: from mail-vw0-f46.google.com ([209.85.212.46]:57871 "EHLO mail-vw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755568Ab0CHQbu convert rfc822-to-8bit (ORCPT ); Mon, 8 Mar 2010 11:31:50 -0500 In-Reply-To: <4B952437.8020607@gmail.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, Mar 8, 2010 at 11:22 AM, jim owens wrote: > David Newall wrote: >> Christian Borntraeger wrote: >>> Some bigger things are missing in the e4defrag tool: >>> ... >>> - overall layout considerations (e.g. putting files close to its >>> directory or >>> =A0 use the atime to move often used files to the beginning of a di= sk etc.) >> >> Shouldn't oft-used files be placed closer to the middle? =A0If you p= lace >> them at the beginning of the file, it's only possible for the head-s= tack >> to be close to the file from the inner direction. =A0Place them in t= he >> middle and it's possible for the head-stack to be close from the out= er >> direction, too, which sounds like a doubling of probability. =A0It s= eems >> that it's the least frequently used files that should be placed at o= ne >> end of the disk or the other. > > No. =A0Your logic would be correct if rotating disks had > similar speed at all locations. =A0Current disks are much > faster at the 0 end than at the middle or highest address. > > It is not unusual to see 2x difference in transfer speed > so you always want the important stuff as low as possible. > > jim Jim, I should know this, but is sector 0 on the outside edge, or the in= ner edge? I assume outer so that the linear speed of the platter under the head is faster and thus more data per second is passing under the head. Greg -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html