[geeks] Linux LVM on iSCSI question

[Dan Duncan]

On Fri, Mar 26, 2010 at 9:33 AM, Patrick Giagnocavo <patrick at zill.net> wrote:
> Agreed that LVM may well be better handled by the external array itself
> in many cases.  However LVM for this solution is used to snapshot the
> running VMs without taking them down, using the kernel's knowledge to
> force consistency on the disks, then snapshotting - they don't have a
> way to snapshot on any other filesystem other than LVM.

LVM is useful for disks on a shared bus.  I've seen a number of
solutions where the LVM volume group can be exported and imported to
pass it around.   For concurrent access you'd need a filesystem that
can be mounted on multiple nodes at once.  (something like GFS)  You
could probably get away with mounting a non-cluster filesystem
read-only on all (or all but one) nodes for hand-off.

> The solution in questions is ProxMox , pretty slick Linux-only
> virtualization (when using OpenVZ and not KVM0 similar to Solaris
> zones/containers.

I notice their description of the storage model says "disable 'use
LUNs direcly' " which implies to me that the storage isn't really
mounted on multiple nodes at once.  Maybe it's using some sort of
hand-off scheme where it exports and then imports the LVM group.

I'll take a look at ProxMox though.  I always like to look at new
virtualization strategies.


--
Dan Duncan