What do you think was the purpose of FreeBSD jail, Virtuozzo and Xen?

https://web.archive.org/web/20011204195446/http://www.sw-sof...

https://web.archive.org/web/20011224040032/http://www.sw-sof...

That's 2001, and Virtuozzo was already advertised supporting migrations.

OpenVZ remained super popular for at least like 10 years after it was open-sourced as OpenVZ in 2005, well into 2015, at least. Primarily because it allowed over-provisioning of RAM and all the other resources, which wasn't possible in other environments without the memory balloon drivers and other issues.

I imagine the major reason OpenVZ has declined in popularity is because nowadays memory is cheap enough that over-provisioning of RAM isn't that much of a selling point, and not being able to run your own kernel with processor-guaranteed virtualisation, is deemed too old-fashioned and less secure for true multitenancy than Linux-KVM, which has basically taken over the entire market, from both Xen and OpenVZ, and VMware, and everybody else. Even Amazon EC2 is based on Linux-KVM now, whereas previously it was based on Xen.