From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753421AbaGTTWL (ORCPT ); Sun, 20 Jul 2014 15:22:11 -0400 Received: from ishtar.tlinx.org ([173.164.175.65]:41097 "EHLO Ishtar.hs.tlinx.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752982AbaGTTWK (ORCPT ); Sun, 20 Jul 2014 15:22:10 -0400 X-Greylist: delayed 2100 seconds by postgrey-1.27 at vger.kernel.org; Sun, 20 Jul 2014 15:22:10 EDT Message-ID: <53CC0EAA.2010202@tlinx.org> Date: Sun, 20 Jul 2014 11:47:06 -0700 From: "Linda A. Walsh" User-Agent: Thunderbird MIME-Version: 1.0 To: Linux-Kernel Subject: Howto tell kernel to use 4096 as granularity & minimum size? Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I have a hard disk with a "512e" sector size: emulated 512, really 4096. The disk returns a 512-byte size to drivers for compatibility. I can partition the disk and setup the allocation size to 4096, but I'd like to tell the kernel to use a virtual-size of 4096 for the sector as an additional performance 'hint', so nothing will even try to use smaller i/o's than that. However, this doesn't seem to work ("# prompt" does mean root): /sys/block/sdd/queue# echo 4096 >minimum_io_size bash: minimum_io_size: Permission denied I realize this is probably implemented as a R-O value, but it there a reason it needs to be if an admin wants to increase it to a multiple of an emulated I/O size so as to have it represent the physical sector size? I.e. if the "/sys" code was patched to allow modification of this variable, would it work for the purpose I am describing (i.e. ignoring emulated 512 size and using the real 4096 size as a minimum (I wouldn't intend or want this to affect the sector# addressing, which would still be done using 512B sector blocks. Thanks!