[Gluster-users] IO performance cut down when VM on Gluster

[Brian Candler]

On Sun, Jan 13, 2013 at 11:55:01PM +0100, Stephan von Krawczynski wrote:
> > 2. Try the 3.4 qa release and native GlusterFS support in the latest 
> > qemu-kvm.
> 
> Thank you for telling the people openly that FUSE is a performance problem
> which could be solved by a kernel-based glusterfs.

No, that's not what he said.

Each KVM virtual machine runs as a userland process. Using libglusterfs, KVM
can talk the gluster protocol natively and thus the client side access
remains entirely in userland.

Putting them through the VFS, either with our without FUSE, is an overhead.

> It is no solution to mess around _inside_ the VM for most people, you simply
> don't want _customers_ on your VM with a glusterfs mount. You want them to see
> a local fs only.

You configure their VM to use a gluster-mounted file as its backing storage. 
This is as invisible to the VM user as (say) iSCSI. You do not need to allow
the user to mount gluster volumes themselves.