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Re: [Xen-users] Re: cLVM on Debian/Lenny

To: Jan Kalcic <jandot@xxxxxxxxxxxxxx>
Subject: Re: [Xen-users] Re: cLVM on Debian/Lenny
From: John Madden <jmadden@xxxxxxxxxxx>
Date: Mon, 20 Apr 2009 14:07:16 -0400
Cc: Olivier Le Cam <Olivier.LeCam@xxxxxxxxxxxxxxxxxxxxx>, Ferenc Wagner <wferi@xxxxxxx>, xen-users@xxxxxxxxxxxxxxxxxxx, Thiago Camargo Martins Cordeiro <thiagocmartinsc@xxxxxxxxx>, Javier Guerra <javier@xxxxxxxxxxx>
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> Now I think I can figure out that there is no difference between a
> domU
> based on a file block device on top of a cluster file system, let's
> suppose OCFS2, and a domU based on physical block device on top of LVM
> (cLVM). In both case, I am eventually able to run the domU on both
> nodes
> having data corruption. Neither OCFS2 nor cLVM with their different
> lock
> managers can provide that mechanism to assure consistency. Right? If
> yes, I would say that the best solution should always be using LVM, at
> least it provides more features.

OCFS2 is a filesystem, LVM is a volume manager.  Don't use the two
products in the same sentence unless it's to say "I formatted an LVM LV
with OCFS2 instead of ext3."  

OCFS2 will allow you to run two domU's (or dom0's, or any host for that
matter) sharing storage and writing to it at the same time without
corruption because it is a cluster filesystem.  You don't need LVM to
accomplish this, either, although you should use it too to manage the


John Madden
Sr UNIX Systems Engineer
Ivy Tech Community College of Indiana

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