@Maescool Could be. Try turning them off. My first guess, though, would be Ubuntu's daemons, e.g., update-apt-xapian-index.
@abananabag I was running 4.4 backport kernel before on that machine, so I'm not 100% sure it's spectre or meltdown.. could also be the new Intel microcode, not sure if I can revert that..
but I'm trying to monitor a bit around what is needing that much IO since upgrade.. (I do see a bit more use by apache)
maescool.be is one server in the network