ext4 and snapshots
The last bullet in slide 20.11 mentions that ext4 supports snapshots.
I have been using linux for several years and this is the first time I heard of it; moreover I was under the impression that snapshots was one of the specific selling points of btrtfs, so I googled a bit.
The only thing that I found was that indeed back in 2011 there were some patches which apparently were almost merged into the kernel - at least it was announced that they would be merged - but in the end they did not. Since then, I can't really find any relevant results. On the contrary, people are actually claiming that they are not supported.
Can anyone shed some light on this?