[linux-lvm] snapshot with bigmem broken

Lauro, John jlauro at umflint.edu
Fri May 16 07:40:02 UTC 2003

> > I did more testing, and it appears that snapshots in LVM will not
> > with either 4GB or or 64GB support enabled in the kernel under
> > This includes both LVM 1.0.7 or the latest LVM2.
> >
> That's a known issue. You are faced with a VM flaw.
> I presume that it's not LVM snapshots only bacause HIGHMEM is
> basically broken.

Can you give more specifics/examples/web links/etc?  Does this mean I
should avoid LVM completely with HIGHMEM?  What if any other problems
should I expect with LVM (and/or other software)?

> > Is there anyone using LVM snapshots with 64GB RAM support (or even
> > RAM support, as snapshots would be good for at least our medium
> > servers if not our large ones)?  Is so, let me know the kernel
> > and LVM version you are using so that I can try it.
> Probably not, because the system lifelocks on bounce buffers (which
> the sympton of the principle HIGHMEM bug).
> Obviously not a lot of HIGHMEM users out there raising priorities to
> this.

Is this easy to reproduce?  If so, how?  Sounds like I am either a
lucky early adopter of a >4GB Libux system, and/or the problem is rare
even on HIGHMEM systems?


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