Citrix Systems 4.2 Cloud Infrastructure Concepts

Chapter 3.
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Cloud Infrastructure Concepts
3.1. About Regions
To increase reliability of the cloud, you can optionally group resources into multiple geographic
regions. A region is the largest available organizational unit within a CloudPlatform deployment. A
region is made up of several availability zones, where each zone is equivalent to a datacenter. Each
region is controlled by its own cluster of Management Servers, running in one of the zones. The zones
in a region are typically located in close geographical proximity. Regions are a useful technique for
providing fault tolerance and disaster recovery.
By grouping zones into regions, the cloud can achieve higher availability and scalability. User
accounts can span regions, so that users can deploy VMs in multiple, widely-dispersed regions.
Even if one of the regions becomes unavailable, the services are still available to the end-user
through VMs deployed in another region. And by grouping communities of zones under their own
nearby Management Servers, the latency of communications within the cloud is reduced compared to
managing widely-dispersed zones from a single central Management Server.
Usage records can also be consolidated and tracked at the region level, creating reports or invoices
for each geographic region.
Regions are visible to the end user. When a user starts a guest VM on a particular CloudPlatform
Management Server, the user is implicitly selecting that region for their guest. Users might also be
required to copy their private templates to additional regions to enable creation of guest VMs using
their templates in those regions.
3.2. About Zones
A zone is the second largest organizational unit within a CloudPlatform deployment. A zone typically
corresponds to a single datacenter, although it is permissible to have multiple zones in a datacenter.