From owner-freebsd-geom@FreeBSD.ORG  Mon Jul 13 09:20:03 2009
Return-Path: <owner-freebsd-geom@FreeBSD.ORG>
Delivered-To: freebsd-geom@hub.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 56DF61065673
	for <freebsd-geom@hub.freebsd.org>;
	Mon, 13 Jul 2009 09:20:03 +0000 (UTC)
	(envelope-from gnats@FreeBSD.org)
Received: from freefall.freebsd.org (freefall.freebsd.org
	[IPv6:2001:4f8:fff6::28])
	by mx1.freebsd.org (Postfix) with ESMTP id 458A18FC14
	for <freebsd-geom@hub.freebsd.org>;
	Mon, 13 Jul 2009 09:20:03 +0000 (UTC)
	(envelope-from gnats@FreeBSD.org)
Received: from freefall.freebsd.org (gnats@localhost [127.0.0.1])
	by freefall.freebsd.org (8.14.3/8.14.3) with ESMTP id n6D9K3ML055033
	for <freebsd-geom@freefall.freebsd.org>; Mon, 13 Jul 2009 09:20:03 GMT
	(envelope-from gnats@freefall.freebsd.org)
Received: (from gnats@localhost)
	by freefall.freebsd.org (8.14.3/8.14.3/Submit) id n6D9K3bL055032;
	Mon, 13 Jul 2009 09:20:03 GMT (envelope-from gnats)
Date: Mon, 13 Jul 2009 09:20:03 GMT
Message-Id: <200907130920.n6D9K3bL055032@freefall.freebsd.org>
To: freebsd-geom@FreeBSD.org
From: Dan Naumov <dan.naumov@gmail.com>
Cc: 
Subject: Re: kern/121481: [gmirror] data rot on disk with gmirror
X-BeenThere: freebsd-geom@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
Reply-To: Dan Naumov <dan.naumov@gmail.com>
List-Id: GEOM-specific discussions and implementations
	<freebsd-geom.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-geom>,
	<mailto:freebsd-geom-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-geom>
List-Post: <mailto:freebsd-geom@freebsd.org>
List-Help: <mailto:freebsd-geom-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-geom>,
	<mailto:freebsd-geom-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 13 Jul 2009 09:20:03 -0000

The following reply was made to PR kern/121481; it has been noted by GNATS.

From: Dan Naumov <dan.naumov@gmail.com>
To: "Steiner, Bernard" <Bernard.Steiner@lahmeyer.de>
Cc: bug-followup@freebsd.org
Subject: Re: kern/121481: [gmirror] data rot on disk with gmirror
Date: Mon, 13 Jul 2009 12:16:33 +0300

 On Mon, Jul 13, 2009 at 11:50 AM, Steiner,
 Bernard<Bernard.Steiner@lahmeyer.de> wrote:
 >> [checksumming utilities]
 >
 > Please explain how to do that on both sides of a gmirror.
 > AFAIK, gmirror can be configured in the following ways:
 > (1) always read from "primary" disk => cannot check secondary
 > (2) round robin or load => read cannot be reliably reproduced
 >
 > Correct me if I am wrong, but this does not seem like a solution
 > to my problem.
 
 You have several options:
 
 Option 1 (this has the benefit of working with all balance algorithms):
 Take disc2 offline, run checksum check (so that checks are done against disc1)
 Take disc2 online, take disc1 offline, run checksum check
 
 Option 2 (for "prefer" algorithm):
 Assuming disk1 is the promoted disk, run checksum check
 Promote disk2, run checksum check
 Promote disk1 to return to original state
 
 - Sincerely,
 Dan Naumov