Section: Software

Entropy

Participants : Jean-Marc Menaud [correspondent] , Fabien Hermenier, Adrien Lèbre, Hien Nguyen Van, Rémy Pottier, Thomas Chavrier, Guillaume Le Louët.

Entropy is a virtual machine (VM) manager for clusters. The current prototype acts as an infinite control loop, which performs a globally optimized placement according to cluster resource usage, scheduler objectives and administrative rules.

Relying on an encapsulation of jobs into VMs, Entropy enables the implementation of finer scheduling policies through cluster-wide context switches, i.e., permutations of VMs present in the cluster. It thus supports a more flexible use of cluster resources and frees end-users from the burden of dealing with time estimates.

The major advantage of the Entropy system concerns the cluster-wide context switch process itself. Entropy computes a new viable configuration and an optimized reconfiguration plan. This plan describes the sequences of transitions to perform (i.e. the run, migrate, suspend/resume, stop VM operations) in order to transit from the current situation to the new one. As the cost of each action and the dependencies between them is considered, Entropy reduces the duration of each cluster-wide context switch by performing a minimum number of actions in the most efficient way.

Around this solution, we developed VMScript, a domain-specific language for administration of virtualized grid infrastructures. This language relies on set manipulation and is used to introspect physical and virtual grid architectures, thanks to query expressions, and notably to modify VM placement on machines. VMScript interacts with Entropy and can be used to define administrative placement rules.

In 2011, Entropy has been integrated into a product of a newly founded start-up EasyVirt (see Sec.  7.1 ). Entropy has also been tested or used by our partners Orange Labs, DGFiP (direction Générale des Finances Publiques), Bull, MACIF, Logica.

Entropy is available under the LGPL license at http://entropy.gforge.inria.fr/ .