Using Burstable Instances in the Public Cloud: Why, When and How?

Abstract

To attract more customers, public cloud providers offer virtual machine (instance) types that trade off lower prices for poorer capacities. As one salient approach, the providers employ aggressive statistical multiplexing of multiple cheaper instances on a single physical server, resulting in tenants experiencing higher dynamism in the resource capacity of these instances. Examples of this are EC2's "type" instances and GCE's "shared-core" instances.We collectively refer to these as burstable instances for their ability to dynamically "burst" (increase the capacity of) their resources. Burstable instances are significantly cheaper than the "regular" instances, and offer time-varying CPU capacity comprising a minimum guaranteed base capacity/rate, which is much smaller than a short-lived peak capacity that becomes available upon operating at lower than base rate for a sufficient duration. Table 1 summarizes our classification of resource capacity dynamism for GCE and EC2 instances along with the nature of disclosure made by the provider. To exploit burstable instances cost-effectively, a tenant would need to carefully understand the significant additional complexity of such instances beyond that disclosed by the providers.