atom feed23 messages in com.redhat.linux-lvmRe: [linux-lvm] Using LVM Mirroring t...
FromSent OnAttachments
Ambrogio De LorenzoSep 16, 2009 6:59 am 
André GillibertSep 16, 2009 8:05 am 
Ambrogio De LorenzoSep 16, 2009 9:47 am 
Brian J. MurrellSep 16, 2009 9:58 am 16, 2009 11:19 am 
Ambrogio De LorenzoSep 16, 2009 12:03 pm 
Ambrogio De LorenzoSep 16, 2009 12:15 pm 
Brian J. MurrellSep 16, 2009 12:49 pm 
André GillibertSep 16, 2009 1:03 pm 
Ambrogio De LorenzoSep 16, 2009 1:22 pm 16, 2009 1:33 pm 
Kai Stian OlstadSep 16, 2009 3:03 pm 
Bryn M. ReevesSep 17, 2009 2:57 am 
Stuart D. GathmanSep 17, 2009 8:06 am 
Brian J. MurrellSep 17, 2009 8:34 am 
Stuart D. GathmanSep 17, 2009 3:49 pm 
Les MikesellSep 17, 2009 4:26 pm 
Brian J. MurrellSep 17, 2009 4:48 pm 
Stuart D. GathmanSep 17, 2009 5:57 pm 
Sven EschenbergSep 17, 2009 6:51 pm 
Stuart D. GathmanSep 17, 2009 6:55 pm 
Mark H. WoodSep 18, 2009 9:05 am 
Stuart D. GathmanSep 18, 2009 12:12 pm 
Subject:Re: [linux-lvm] Using LVM Mirroring to obtain a usable backup
From:Ambrogio De Lorenzo (
Date:Sep 16, 2009 12:15:40 pm

Il giorno mer, 16/09/2009 alle 12.58 -0400, Brian J. Murrell ha scritto:

On Wed, 2009-09-16 at 18:47 +0200, Ambrogio De Lorenzo wrote:

snapshot is not a good choise for me.

It actually is. I snapshot all of my filesystems before every upgrade and let the snapshots hang around until I am happy with the upgrade.

Imagine that upgrade change something in LVM configuration or in lvm software. Snapshots are good only if you have the original data and all the modified data. This is not a good way to rollback everything.

My idea is: 1. Insert a new disk via USB 2. configure mirroring 3. continue to work and monitor for mirroring progress (performance are not a problem) 4. In a good moment shutdown the system 5. boot with a live CD with an LVM version compatible 6. split mirroring of lv (this made available 2 copies with different names on 2 different disks) 7. split VG 8. reboot without the USB disk (that is a good copy of original VG) 9. change everything I need (i.e. I can also destroy disk or destroy VG) and test it. 10. If is good I can destroy the USB copy, if it isn't I can boot from USB

Well, snapshots give you a very space efficient (if not performance efficient due to the COW nature of snapshots) version of that. When you create a snapshot and before your modify any data in the origin (the volume you are creating a snapshot (a.k.a. copy) of your snapshot is an identical copy (just as if you'd used dd) of the origin, without using any additional space even!

I know very well how snapshot works. And it's for this reason that I don't think it's a good choise for my scope

I'm looking also on mdadm to mirror a disk (or partition) but I think it is not usable when disk is already partitioned and used without mdadm.

Well, you will have that same problem with LVM. Planning is key in any of this.

Yes, but LVM is already configured for this reason. Mdadm isn't. I tried to test it but I'm not able to obtain a mirror of an already partitioned and used disk.

Bye Ambrogio