Protecting Critical Systems - For the purposes of this course, we will use the following terms to define the levels of protection.
Fault Tolerance - Eliminating single points of failure
High Availability - Protecting critical systems with multiple safeguards with the goal of 100 percent uptime
Disaster Recover & Business Continuity - In the event that a site is not available, another site can take over operations at some defined capacity

Protecting XenServer

Component	Fault Tolerance	High Avaialability	Disaster Recovery & Business Continuity
XenServer Hosts	Have a minimum of two	Make sure full load can run on one less server	Create second site with hosts based on needed capacity
Networking	Create NIC bonds with multiple NICs	Have multiple NICs with multiple paths to multiple switches	Create identical configuration in a second site
Storage	Multipath storage	Replicated SAN	Remote site replication (StorageLink)
Metadata	Built-in replication between servers	Built-in replication between servers	Export and keep available for import. Maintain a secondary site.

Protecting Provisioning Services

Component	Fault Tolerance	High Avaialability	Disaster Recovery & Business Continuity
Data Store	Protect with SQL replication.	Protect with SQL replication.	Replicate data store to remote site.
Provisioning Services	Have at least two servers configured with all VHD files available from either server	Configure all VHDs to use high availability built-in Provisioning Services.	Create a second site to add to vDisk distribution.

Note: For information about configuring Provisioning Services to automatically balance the target device load between servers, see Citrix eDocs at eDocs.citrix.com

Protecting XenApp

Component	Fault Tolerance	High Avaialability	Disaster Recovery & Business Continuity
XenApp Controllers	Create at least two XML Brokers.	Protect XML Broker #1. Restart XML Broker #2 if possible.	Create a second site with Zone Data Collector and at least one XML Broker.
XenApp servers in a worker group	Create at least two XenApp servers in a worker group and make sure that no application is only available on only one server.	Set at least one XenApp servers in a worker group to "protected."	Create a second site. If using Provisioning Services, replicate VHDs.
Web Interfaces	Deploy multiple Web Interface servers.	Protect Primary. Restart Secondary if possible.	Maintain Web Interface servers across multiple sites. Can be front-ended by Global Server Load Balancing.
Data Store	Protect with SQL replication.	Protect	Replicate data store to remote site.

Protecting XenDesktop

Component	Fault Tolerance	High Avaialability	Disaster Recovery & Business Continuity
Desktop Delivery Controllers	Deploy multiple Desktop Delivery Controllers.	Protect XML Broker #1. Restart XML Broker #2 if possible.	Maintain Desktop Delivery Controllers in multiple sites.
Web Interfaces	Deploy multiple Web Interface servers.	Protect Primary. Restart Secondary if possible.	Maintain Web Interface servers across multiple sites. Can be front-ended by Global Server Load Balancing.
Data Store	Protect with SQL replication.	Protect	Replicate data store to remote site.
Hosted Desktops	Ensure that there are enough images to support all end users.	Do not restart.	Replicate as part of Provisioning Services and Desktop Delivery Controller.

For more information about High Availability for Desktop Virtualization, see Citrix article CTX123245