VM vs Container Xen, KVM, VMware, etc. ● Hardware emulation / paravirtualization ● Can run different OSs on the same box ● Dozens of instances ● OS sprawl problem ● Lower performance ● Chroot on steroids ● Single OS per box+ ● Hundreds of instances ● Dynamic resource management, best scalability ● No performance overhead

OpenVZ vs. Xen comparison by HP labs ● “For all the configurations and workloads we have tested, Xen incurs higher virtualization overhead than OpenVZ does.” ● “For all the cases tested, the virtualization overhead observed in OpenVZ is low, and can be neglected in many scenarios.” ● “The two nodes running Xen become overloaded when hosting four instances of RUBiS, whereas those using OpenVZ can host at least six without being overloaded.” From

New Stuff ● RHEL6 kernel port ● VSwap: easy management, RSS reclamation ● Containers CPU binding (cpumask) ● PCI device delegation ● NFS mounts migration ● Journaled quota ● ext4 safe writeback

Future directions ● Mainstream kernel integration ● Container in a file a.k.a. PLOOP – Come to see our talk! ● CRIU: checkpoint/restore in userspace ● Caching de-duplicating FS (pfscache)

Mainstream kernel integration ● OpenVZ project pioneers container technology – Developing new container technology since Features then ported from OpenVZ to upstream Linux “containers”. ● Already upstream (in Linux containers): – IPC namespace, utsname() virtualization, PID namespace, user namespace, cgroups (control groups), Memory controllers (RSS, page cache), Network namespace... – Collaborative community effort: IBM, Google, SGI, Parallels, and many others. ● It's still ongoing – In progress: NFS virtualization, network buffer accounting, Checkpoint/restart in userspace – TODO: Kernel memory accounting,...

To sum it up ● Containers scale as well as Linux does – Benefit from all Linux performance improvements – Native I/O speed, best possible performance – The more memory/CPUs the merrier ● Platform-independent – as long as Linux supports it, we support it – arm/mips/ppc no problem. ● Plays well with others (Xen, KVM, VMware) – VM and container technologies are orthogonal – run containers and VMs side by side