From mboxrd@z Thu Jan  1 00:00:00 1970
Subject: Re: [linux-lvm] pvmove root filesystem?
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In-Reply-To: <20011101235041.B746@lynx.no>; from adilger@turbolabs.com on Thu, Nov 01, 2001 at 11:50:43PM -0700
From: Joe Thornber <thornber@btconnect.com>
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Date: Fri Nov  2 05:20:02 2001
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On Thu, Nov 01, 2001 at 11:50:43PM -0700, Andreas Dilger wrote:
> On Nov 02, 2001  00:33 -0500, Brian J. Murrell wrote:
> > > Brian, the "pvmove" mechanism is not yet 100% safe for mounted filesystems.
> > 
> > Ugh.  I was hoping to not hear something like this.  Has it gotten any
> > better recently?  What I mean is my LVM identifies itself as:
> > 
> > LVM version LVM 0.9.1_beta7(ish)  by Heinz Mauelshagen  (20 June 2001)
> > lvm -- Module successfully initialized
> 
> Well, there have been a lot of changes to the pvmove locking code and
> such since then.  Whether it actually makes a difference is hard to
> tell.
> 
> > Am I going to run into even more problems with this verion of LVM vs.
> > the latest or has the "live" pvmove stuff not changed much between the
> > version I am running and current.
> 
> Nobody has really done any good testing on it.

I've done a bit of testing, and have never seen any problems due to
the holes in the locking; as such I am happy to use pvmove on *my*
development system (I don't use raw devices).  I certainly couldn't
recommend it for production systems.

As well as the locking problems there is a potential kernel deadlock,
which I can easily induce under memory pressure (too much deferred io
that cannot complete and no free memory to enable the userland copy to
finish).

- Joe