> When they first started they used FreeBSD jails IIRC.
Nope. Solaris Zones.
Incorrect. FreeBSD was in use first, as founder David Young’s own history [1] describes. OpenSolaris and zones came later.
[1]: https://www.google.co.uk/amp/s/davidpaulyoung.com/2016/06/17...
When they first started they used FreeBSD jails IIRC.
The main selling point is/was being closer to the hardware and thus getting better hardware utilization. Virtualizing at the machine level was a lot slower (especially before Intel VT-x and AMD-V came along) and so one wouldn't lose (say) 30% right off the top:
* https://en.wikipedia.org/wiki/OS-level_virtualisation