CloudSSI: revisiting SSI in cloud era

The current IaaS model has several shortcomings. First, several IaaS providers only offers VM (virtual machine) with predefined sizes, thus enterprise tenants must judiciously determine the VM size that best fit their application. This is challenging as overprovisioning VMs can lead to waste of resources while underprovisioned VMs can lead to poor performance. Second, when an application requires more resources than a VM can provide, tenants are currently limited to either scaling-out or scaling-up their applications. However, in both situations the granularity is at the level of VMs which leads to sizing issues discussed earlier. Third, scaling-up is ineffective as it incurs a significant amount of downtime/poor performance while the new VM is being provisioned and not all applications support scaling-out. For example while, Web servers can be easily scaled-out other legacy applications can not [1], thus limiting its applicability.