It is based on illumos an OpenSolaris operating system.
- There is only one OS, and for practical purposes it is read-only
- You boot from a USB stick. Want to upgrade your OS? Pop in a new USB stick. I can’t overstate the fundamental rightness of that.
- In all other respects, each zone or container is its own virtual machine, with its own network interfaces, etc., isolated from the rest of the universe
- You get bare-metal performance from your hardware - no emulation, no virtual I/O driver talking to a real I/O driver, no extra memory copies getting data in or out
- You can do a lot more with minimal hardware than you could if you were running full-blown virtualization (though SmartOS supports KVM, so if you want Linux VMs you can have them)
- Each zone is its own ZFS volume - so you get a bulletproof, enterprise grade filesystem with redundancy, snapshots you can zap over to another machine for management