Have NextCloud 13 Snap running on a Ubuntu 17.10 Virtual machine, VM is running on older hardware (Opteron G2) and using fairly slow HDD’s but still the performance is terrible, I created a sharing link just down and it took 24 seconds for the page to load once the link was clicked.
VM has 6gb ram and 4 cores - host node is mostly idle as it’s just a personal box.
following my experience, VM sometimes are nightmares when talking about perf.
For exemple, on my I7 system using Oracle VM, a debian 2 core is faster than a 4 core setup !
If using option sata controller + scsi controller in same VM, i loose around 50% of write speed…
VM are good to setup conf but forget about fine tune !