Disaster recovery in cloud computing: a survey <s> DT Enabled Cloud Architecture <s> Cloud computing systems fundamentally provide access to large pools of data and computational resources through a variety of interfaces similar in spirit to existing grid and HPC resource management and programming systems. These types of systems offer a new programming target for scalable application developers and have gained popularity over the past few years. However, most cloud computing systems in operation today are proprietary, rely upon infrastructure that is invisible to the research community, or are not explicitly designed to be instrumented and modified by systems researchers. In this work, we present Eucalyptus -- an open-source software framework for cloud computing that implements what is commonly referred to as Infrastructure as a Service (IaaS); systems that give users the ability to run and control entire virtual machine instances deployed across a variety physical resources. We outline the basic principles of the Eucalyptus design, detail important operational aspects of the system, and discuss architectural trade-offs that we have made in order to allow Eucalyptus to be portable, modular and simple to use on infrastructure commonly found within academic settings. Finally, we provide evidence that Eucalyptus enables users familiar with existing Grid and HPC systems to explore new cloud computing functionality while maintaining access to existing, familiar application development software and Grid middle-ware. <s> BIB001 </s> Disaster recovery in cloud computing: a survey <s> DT Enabled Cloud Architecture <s> The advances of virtualization technology in Data Centres lead to the development of features such as High Availability, Disaster Recovery and Fault Tolerance. However, Infrastructure as a Service (IaaS) computing clouds that span across distributed areas require even a more advanced mechanism. In this paper we present a Disaster Tolerance (DT) enablement solution that covers all layers of IaaS clouds. Technical aspects of implementation are highlighted, detailing the Seven-stage DT algorithm and the enhancements of Qemu-kvm hypervisor, Libvirt virtualization toolkit, Eucalyptus cloud and the Amazon Elastic Compute Cloud (EC2) public API and tools. <s> BIB002
It is an extended architecture based on Romulus seven stage algorithm. It uses a hierarchical tree architecture BIB002 based on the Eucalyptus IaaS architecture BIB001 ). It provides a disaster tolerant service with respect to resource allocation issue which is a challenge in DT services. Host and backup clusters are monitored by high availability controllers. Each cluster has three different controllers:  Storage controller: To control and manage the cluster storage.  Cluster controller: To manage IPs, centralized memory and CPU availability. In this system, VM failover consists of two scenarios. The first scenario is cluster failure. In this situation, backup cluster will be activated. Node failure is another scenario in which cluster controller releases VMs' IP and allocates a backup node to compose required VMs. This system is most useful for extended distance and metropolitan clusters because of low latency requirements.