Tuesday, January 03, 2012

Live Migration Optimization for VM Running Large Enterprise Applications



The problem with  Enterprise class application:

  • Bigger than average resource requirement
  • Average SAP ERP 16GB + per VM with 32 GB of swap more than common
  • OLTP system such as ERP are very sensitive to time variation. 
  • Rely heavily on precise scheduling capabilities, triggers, timers and on the ACID compliance of the underlying

As a result there is many challenge when migrating VMs running such application:

  • Disconnection of services: 
    • Gigabit Ethernet timeout  ≈ 5 seconds (>500 MB memory left in stop and copy phase )
    • Downtime is workload dependent
  • Disruption of services:
    • Migration progressively increasing the amount of resource dedicated to itself => gradually degrade performance of the coexisting systems / VMs.
    • Difficulty to maintain consistency and transparency
  • Unpredictability and rigidity

With some of my colleague we developed optimisation that enables a smother migration of such system while reducing the overall down time and virtually eliminating any disruption of services.

You can watch the video explaining the change we are proposing Here of the presentation at KVM forum :



And download the slide deck there:  http://www.linux-kvm.org/wiki/images/c/cb/2011-forum-kvm_hudzia.pdf