An availability zone is the largest organizational unit within a CloudStack environment and is shown in the Figure 5-12. A data center will usually contain a single zone but may contain more than one. By structuring CloudStack into geographical zones, virtual instances and data storage can be placed in specific locations in order to comply with an organization’s data storage policies for performance or geographical optimization. This can also be utilized for regulatory compliance reasons where storage/compute must be kept within a certain geographical boundary.