From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.redhat.com (mx1.redhat.com [172.16.48.31]) by int-mx1.corp.redhat.com (8.11.6/8.11.6) with ESMTP id i9S6Zir07064 for ; Thu, 28 Oct 2004 02:35:44 -0400 Received: from percy.comedia.it (percy.comedia.it [212.97.59.71]) by mx1.redhat.com (8.12.11/8.12.11) with ESMTP id i9S6ZabS015298 for ; Thu, 28 Oct 2004 02:35:42 -0400 Date: Thu, 28 Oct 2004 08:35:31 +0200 From: Luca Berra Subject: Re: [linux-lvm] Software raid on top of lvm logical volume Message-ID: <20041028063530.GA13279@percy.comedia.it> References: <41801ADE.6030308@monjoin.net> <20041028011738.GD13737@kluge.net> <41808B37.40406@monjoin.net> Mime-Version: 1.0 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <41808B37.40406@monjoin.net> Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="iso-8859-1"; format="flowed" To: LVM general discussion and development On Thu, Oct 28, 2004 at 08:01:27AM +0200, Eric Monjoin wrote: >Theo Van Dinter a =EF=BF=BDcrit : > >Well it's because we have problems in this way. We have a server=20 >connected to 2 EMC Symmetrix where we assign some 70Gb and 40Gb Luns. =20 >We used Powerpath to manage the dual path to the Luns and so I first=20 >created mirror as this : >But after a while I obtain that : >Personalities : [raid1] >read_ahead 1024 sectors >Event: 10 =20 >md9 : active raid1 [dev e9:31][1] [dev e8:e1][0] > 42829184 blocks [2/2] [UU] >and if we try to rebuild the mirror after after loosing access to one of=20 this might be a problem with powerpath, it seems harmless tough >the EMC, we have really bad result : >Personalities : [raid1] >read_ahead 1024 sectors >Event: 26 =20 >md9 : active raid1 emcpowerd1[2] [dev e8:e1][0] > 42829184 blocks [2/1] [U_] > [>....................] recovery =3D 1.4% (630168/42829184)=20 >finish=3D68.1min speed=3D10315K/sec this is a problem with linux md raid. it does not support fast resync with a bitmap of changed sectors, there is a project to implement it, but it is not yet in the standard kernel. look on the linux-raid mailing list archives for something called 'fast raid 1'. i do not believe you would have any advantage in stacking md above lvm anyway. Regards, Luca --=20 Luca Berra -- bluca@comedia.it Communication Media & Services S.r.l. /"\ \ / ASCII RIBBON CAMPAIGN X AGAINST HTML MAIL / \