Haizea is an open source lease management architecture that OpenNebula can use as a scheduling backend. Haizea can also be run in simulation, providing a platform for experimenting with scheduling algorithms that depend on VM (Virtual Machine) deployment or on the leasing abstraction. Haizea uses leases as a fundamental resource provisioning abstraction, and implements those leases as virtual machines, taking into account the overhead of using virtual machines (e.g., deploying a disk image for a VM) when scheduling leases. Using OpenNebula with Haizea allows resource providers to lease their resources, using potentially complex lease terms, instead of only allowing users to request VMs that must start immediately.

One of the types of lease implemented by Haizea is advance reservation of capacity. Other VM management solutions and cloud providers like Amazon EC2, Flexiscale or ElasticHost use immediate, where VMs mu st be allocated right away or not at all, or best-effort, where VMs state pending until resource allocation, provisioning models. Service provisioning clouds have requirements that cannot be supported only with an immediate provisioning model, such as resource requests that are subject to non-trivial policies and capacity reservations at specific times to meet peak capacity requirements. They want to rely on advance reservation in order to ensure the service workload can be executed at the provider’s site. Additionally, smaller clouds with limited resources, where not all requests may be satisfiable immediately for lack of resources could benefit from more complex VM placement strategies supporting queues, priorities, and advance reservations. Advance reservation is also required for co-allocation of service components within or across cloud providers.

I recommend the post on Haizea and Private Clouds written by Borja Sotomayor, author of Haizea, to know more details about this useful technology and its position in the Cloud ecosystem.