A Virtual Infrastructure Layer for Cluster and Grid Computing

Ignacio Martin Llorente

Cluster, and so Grid site, administrators have to deal with the following requirements when configuring and scaling their infrastructure:

• Heterogeneous configuration demands. Users often require specific versions of different software components (e.g. operating system, libraries or post-processing utilities). The cost of the installation, configuration and maintenance of user-specific or VO-specific worker nodes limits the flexibility of the infrastructure.
• Performance partitioning. Most of the computing infrastructures do not allow administrators to isolate and partition the performance of the physical resources  they devote to different computing clusters or Grid infrastructures. This limits the quality of service and reliability of actual computing platforms, preventing a wide adoption of the Grid paradigm.

In order to overcome these challenges, we propose a new virtualization layer between the service and the physical infrastructure layers, which seamless integrates with existing Grid and cluster middleware stacks. The new virtualization layer extends the benefits of VMMs (Virtual Machine Monitors) from a single physical resource to a cluster of resources, decoupling a server not only from the physical infrastructure but also from the physical location. In the particular case of computing clusters, this new layer supports the dynamic execution of  computing services, working nodes, from different computer clusters on a single physical cluster.

OpenNebula is the name of a new open-source technology that transforms a physical infrastructure into a virtual infrastructure by dynamically overlaying VMs over physical resources. So computing services, such as working nodes managed by existing LRMs (Local Resource Managers) like SGE, Condor, OpenPBS..., could be executed on top of the virtual infrastructure; so allowing a physical cluster to dynamically execute multiple virtual clusters.

The separation of resource provisioning, managed by OpenNebula, from job execution management, managed by existing LRMs, provides the following benefits:

• Cluster consolidation because multiple virtual working nodes can run on a single physical resource, reducing the number of physical systems and so space, administration, power and cooling requirements. The allocation of physical resources to virtual nodes could be dynamic, depending on its computing demands, by leveraging the migration functionality provided by existing VMMs
• Cluster partitioning because the physical resources of a cluster could be used to execute virtual working nodes bound to different virtual clusters
• Support for heterogeneous workloads with multiple (even conflicting) software requirements, allowing the execution of software with strict requirements as jobs that will only run with a specific version of a library or legacy application execution

Consequently, this approach provides the flexibility required to allow Grid sites to execute on-demand VO-specific working nodes and to isolate and partition the physical resources. Additionally, the architecture offers other benefits to the administrator of the cluster, such as high availability, support for planned maintenance and changing capacity availability, performance partitioning, protection against malicious use of resources...

The idea of a virtual infrastructure which dynamically manages the execution of VMs on physical resources is not new. There exist several VM Management proprietary solutions to simplify the use of virtualization, so providing the enterprise with the potential benefits this technology may offer. Examples of products for the centralized management of the life-cycle of a VM workload on a pool of physical resources are: Platform VM Orchestrator, IBM Virtualization Manager, Novell ZENworks, VMware Virtual Center, and HP VMManager.

The OpenNebula Virtual Infrastructure Engine differentiates from those VM management systems in its highly modular and open architecture  to meet the requirements of cluster administrators. The OpenNebula Engine provides a command line interface for monitoring and controlling VMs and physical resources quite similar to that provided by well-known LRMs. Such interface allows its integration with third-party tools, such as LRMs, service adapters, VM image managers...; to provide a complete solution for the deployment of flexible and efficient computing clusters. The service layer decoupling from the infrastructure layer allows an straightforward extension of the previous idea to any kind of service. In this way any physical infrastructure can be transformed into a very effective provisioning platform.

A Technology Preview of OpenNebula is available for download under the terms of the Apache License, version 2.0.

Ignacio Martín Llorente
Reprinted from blog.dsa-research.org