From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753156Ab3KDKZd (ORCPT ); Mon, 4 Nov 2013 05:25:33 -0500 Received: from mail-gg0-f179.google.com ([209.85.161.179]:44565 "EHLO mail-gg0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750946Ab3KDKZb (ORCPT ); Mon, 4 Nov 2013 05:25:31 -0500 From: "Justin Piszcz" To: , Subject: 3.12: raid-1 mismatch_cnt question Date: Mon, 4 Nov 2013 05:25:28 -0500 Message-ID: <000f01ced948$2fbab140$8f3013c0$@lucidpixels.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 14.0 Thread-Index: Ac7ZSAghnp84jgcPQpKT/JB6XBqEMw== Content-Language: en-us Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, I run two SSDs in a RAID-1 configuration and I have a swap partition on a third SSD. Over time, the mismatch_cnt between the two devices grows higher and higher. Once a week, I run a check and repair against the md devices to help bring the mismatch_cnt down. When I run the check and repair, the system is live so there are various logs/processes writing to disk. The system also has ECC memory and there are no errors reported. The following graph is the mismatch_cnt from June 2013 to current; each drop represents a check+repair. In September, I dropped the kernel/vm caches before running check/repair and that seemed to help a bit. http://home.comcast.net/~jpiszcz/20131104/md_raid_mismatch_cnt.png My question is: is this normal or should the mismatch_cnt always be 0 unless there is a HW or md/driver issue? Justin.