[contrail | sla]

Cloud issues addressed

Current Cloud offerings are mostly at the level of best effort. This may or may not be sufficient for your application needs. Service Level Agreements (SLAs) can help here, as they would allow for a more differentiated approach to get Cloud services that fit requirements. In a federated Cloud, with different resources providers, each with a different SLA offering, and probably different pricing structures, a way to select the correct ones becomes even more urgent.

The growth of cloud providers in the last few years, both in terms of number of players and of differentiation of offered services, forces companies to deal with a not trivial selection problem. Even existing cloud brokers don't offer an effective solution to the issue of identifying the ideal cloud provider for each application of their customers.

Different cloud providers may have different interfaces to specify requirements, and not all of them provide automatic quotation for a required user configuration. Interacting with different providers by hand to find the best and cheapest one for a given application is a complex and time consuming task.

Contrail's Solution

Contrail-SLA implements basic SLA functionality for Cloud computing on resource provider level and on a Cloud federation level. It implements SLA template creation, browsing and querying. It also provides SLA execution planning and adjustment. Contrail SLA is based on SLA@SOI, which is compliant to WS-Agreement, and extends it by integrating with Open Virtualization Format (OVF) which is used to describe the application. Accounting is implemented at all levels.

The Contrail federation SLA Management layer automates the provider comparison and selection task and hides to the final user the complexity of interacting with multiple cloud providers.

The Contrail SLA Management layer allows expressing user requirements about application Quality of Service (QoS) in a uniform way. The same SLA syntax is used by all cloud providers in the federation, enabling it to negotiate with and to compare multiple providers. To enable negotiation interoperability of different cloud providers with the Contrail federation, a SLA Management layer is added to each provider.

SLA terms that are supported by Contrail include specific characteristics defining the configuration of each VM,  such as the amount of memory or the number of virtual cores, but also terms related to application setup, such  as the possibility to reserve resources; there are terms affecting performance, such as the possibility to co-locate in the same physical host different VMs that must exchange large amounts of data, and even terms important at a legal or privacy level, such as those defining the geographical location of resources.

Features incude:

  • SLA template repository
  • Automatic multi-step SLA negotiation
  • SLA-based provider selection
  • SLA monitoring and violation detection
  • Support for defining enforcement rules
  • Geographic and security-level  SLA terms
  • Reservation and VM-placement SLA terms
  • Support for elasticity / 
automatic scaling

More information

  • Documentation: CONTRAILSCHOOL-SLA .pdf