**Abstract**

Cloud computing provides resources by using virtualization technology and a pay-as-you-go cost model. Network Functions Virtualization (NFV) is a concept, which promises to grant network operators the required flexibility to quickly develop and provision new network functions and services, which can be hosted in the cloud. However, cloud computing is subject to failures which emphasizes the need to address user's availability requirements. Availability refers to the cloud uptime and the cloud capability to operate continuously. Providing highly available services in cloud computing is essential for maintaining customer confidence and satisfaction and preventing revenue losses. Different techniques can be implemented to increase the system's availability and assure business continuity. This chapter covers cloud computing as business continuity solution and cloud service availability. This chapter also covers the causes of service unavailability and the impact due to service unavailability. Further, this chapter covers various ways to achieve the required cloud service availability.

**Keywords:** Cloud Computing, Business Continuity (BC), Disaster Recovery (DR), Network Functions Virtualization (NFV), Virtual Machine (VM), High Availability, Failover, Private Cloud, Hybrid Cloud, Public Cloud, Recovery Time Objective (RTO), Recovery Point Objective (RPO), IaaS, Paas, Saas, DRaaS
