From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx3.redhat.com (mx3.redhat.com [172.16.48.32]) by int-mx2.corp.redhat.com (8.13.1/8.13.1) with ESMTP id m8GJuSbu000933 for ; Tue, 16 Sep 2008 15:56:29 -0400 Received: from smtp2-g19.free.fr (smtp2-g19.free.fr [212.27.42.28]) by mx3.redhat.com (8.13.8/8.13.8) with SMTP id m8GJuGDd020278 for ; Tue, 16 Sep 2008 15:56:16 -0400 Received: from smtp2-g19.free.fr (localhost.localdomain [127.0.0.1]) by smtp2-g19.free.fr (Postfix) with ESMTP id 902F112B7D9 for ; Tue, 16 Sep 2008 21:56:14 +0200 (CEST) Received: from [192.168.1.2] (bon31-1-82-66-78-161.fbx.proxad.net [82.66.78.161]) by smtp2-g19.free.fr (Postfix) with ESMTP id E4B1212B82C for ; Tue, 16 Sep 2008 21:56:01 +0200 (CEST) Message-ID: <48D00F51.5090305@free.fr> Date: Tue, 16 Sep 2008 21:56:01 +0200 From: Georges Giralt MIME-Version: 1.0 Subject: Re: [linux-lvm] Mirrored LV References: <1221592827.6037.57.camel@localhost> In-Reply-To: <1221592827.6037.57.camel@localhost> Content-Transfer-Encoding: quoted-printable 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 Koen Vermeer a =EF=BF=BDcrit : > Hi, >=20 > I was thinking of using a mirrored LV as a easier to use alternative to > a RAID1 PV (with matching VG and LV). I tried to find the information I > need on how this works and how to set it up, but so far, I failed. >=20 > First, am I right in trying to use LVM in this way? I have two disks, > and I just want to mirror some LVs. >=20 > Second, I am confused by the apparent need to have this log stored on > another device. Actually, this doesn't seem true in two ways: There's > the option of having the log in memory and then the documentation only > says that the log is 'usually on a separate device'. Does that mean that > using a mirrored LV makes no sense on a system with two disks? Or should > I just keep the log in memory in this case? Or can I use another PV on > one of the disks? Should this be mirrored as well? What happens if I > loose that data? >=20 >>>From what I found when searching for answers, it seems that I'm not the > only one that's confused... But maybe my searching skills are just > lacking. Anyway, I appreciate any help and insights! >=20 > Best, > Koen Koen, I confirm that you have to use 3 disks to mirror a VG with the actual=20 version of software. At home, having enough disk, I use 3 disks to get my VG/LV mirrored and=20 it works flawlessly since a couple of years. At work, we have mirrored the PV using 2 devices and the software RAID=20 (md) and build the VG/LV on top of that. It runs flawlessly for 4 years=20 I think (have to check the exact installation date...) So choice is yours... HAve a nice day. P.S. At home, I do not use the whole PV for my LV. Each PV is split in two dissymitrical parts : a small 100 M partition=20 and the rest of the device. The small partition is used for a software=20 RAID (md) to hold the /boot. The rest of the disk as a regular PV used=20 to build the mirrored VG/LV. This way, if one disk breaks I still can=20 boot onto the remaining one. Of course, it is a manual boot but easier=20 compared to searching a useable rescue CD and the correct kernel=20 version. Think about it. --=20 If the only tool you have is a hammer, you tend to see every problem as=20 a nail. Abraham Maslow