On Wed, Jun 08, 2011 at 08:52:33PM -0700, Andrew Morton wrote: > > > This sort of thing could be implemented in userspace and wired up via > > > fuse, I assume. Has that been attempted and why is it inadequate? > > > > I think that would be a valid question if the proposal was large and > > complex. But overlayfs is really quite small and self-contained. > > Not merging it would be even smaller and simpler. If there is a > userspace alternative then that option should be evaluated and compared > in a rational manner. For the Ubuntu liveCD we have tried to use unions via fuse with a view to dropping aufs2 as an external module. The performance was atrocious (IIRC of the order of 10x slower), to the point that most people assumed it was broken and reset the machine. The other use case I have seen here have been for package builders on which a virgin chroot has a writable layer dropped on top, allowing simple undo at the end of the build. I have heard of people wanting to use this for root filesystems for virtual machines as well. We have done quite a bit of testing with liveCDs built to use overlayfs with a view to switching over, and have been very impressed with its stability. It is also pleasing to see an implementation which is small enough to actually understand. -apw -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
