The resources leased to a guest may span multiple sites and may include a diversity of resource types in differing quantities. Each SHARP resource has a type with associated attributes that characterize the function and power of instances or units of that type. Resource units with the same type at a site are presumed to be interchangeable.
Each lease binds a set of resource units from a site (a resource set) to a guest for some time interval (term). A lease is a contract between a site and a service manager: the site makes the resources available to the guest identity for the duration of the lease term, and the guest assumes responsibility for any use of the resources by its identity. In our current implementation each lease represents some number of units of resources of a single type.
Resource attributes define the performance and predictability that a lease holder can expect from the resources. Our intent is that the resource attributes quantify capability in an application-independent way. For example, a lease could represent a reservation for a block of machines with specified processor and memory attributes (clock speed etc.), or a storage partition represented by attributes such as capacity, spindle count, seek time, and transfer speed. Alternatively, the resource attributes could specify a weak assurance, such as a best-effort service contract or probabilistically overbooked shares.