[linux-lvm] pvmove root filesystem?
Joe Thornber
thornber at btconnect.com
Fri Nov 2 05:20:02 UTC 2001
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
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