Product Documentation

Zones

Feb 24, 2016

Deployments that span widely-dispersed locations connected by a WAN can face challenges due to network latency and reliability. There are two options that mitigate those challenges:

  • Deploy multiple Sites, each with their own SQL Server Site database.

This option is recommended for large enterprise deployments. Multiple Sites are managed separately, and each requires its own SQL Server Site database. Each Site is a separate XenApp deployment.

  • Configure multiple zones within a single Site.

Configuring zones can help users in remote regions connect to resources without necessarily forcing their connections to traverse large segments of the WAN. Using zones allows effective Site management from a single Citrix Studio console, Citrix Director, and the Site database. This saves the costs of deploying, staffing, licensing, and operating additional Sites containing separate databases in remote locations.

Zones can be helpful in deployments of all sizes. You can use zones to keep applications and desktops closer to end users, which improves performance. A zone can have one or more Controllers installed locally for redundancy and resiliency, but it is not required.

Throughout this article the term local refers to the zone being discussed. For example, "A VDA registers with a local Controller" means that a VDA registers with a Controller in the zone where the VDA is located.

Zones in this release are similar, but not identical to zones in XenApp version 6.5 and earlier. For example, in this implementation of zones, there are no data collectors. All Controllers in the Site communicate with one Site database in the primary zone. Also, failover and preferred zones work differently in this release.

Zone types

A Site always has one primary zone. It can also optionally have one or more satellite zones. Satellite zones can be used for disaster recovery, geographically-distant datacenters, branch offices, a cloud, or an availability zone in a cloud.

Primary zone

The primary zone has the default name "Primary," which contains the SQL Server Site database (and high availability SQL servers, if used), Studio, Director, Citrix StoreFront, Citrix License Server, and NetScaler Gateway. The Site database should always be in the primary zone.

The primary zone should also have at least two Controllers for redundancy, and may have one or more VDAs with applications that are tightly-coupled with the database and infrastructure.

Satellite zone

A satellite zone contains one or more VDAs, Controllers, StoreFront servers, and NetScaler Gateway servers. Under normal operations, Controllers in a satellite zone communicate directly with the database in the primary zone.

A satellite zone, particularly a large one, might also contain a hypervisor that is used to provision and/or store machines for that zone. When you configure a satellite zone, you can associate a hypervisor or cloud service connection with it. (Be sure any Machine Catalogs that use that connection are in the same zone.)

A Site can have different types of satellite zones, based on your unique needs and environment. The following figure illustrates a primary zone and examples of satellite zones.  

localized image
  • The Primary zone contains two Controllers, Studio, Director, StoreFront, License Server, and the Site database (plus high availability SQL Server deployments). The Primary zone also contains several VDAs and a NetScaler Gateway.
  • Satellite zone 1 - VDAs with Controller

Satellite zone 1 contains a Controller, VDAs, and a StoreFront server.  VDAs in this satellite zone register with the local Controller. The local Controller communicates with the Site database and license server in the primary zone.

If the WAN fails, the connection leasing feature allows the Controller in the satellite zone to continue brokering connections to VDAs in that zone. Such a deployment can be effective in an office where workers use a local StoreFront site and the local Controller to access their local resources, even if the WAN link connecting their office to the corporate network fails.

  • Satellite zone 2 - VDAs with redundant Controllers

Satellite zone 2 contains two Controllers, VDAs, and a StoreFront server. This is the most resilient zone type, offering protection against a simultaneous failure of the WAN and one of the local Controllers.

Where VDAs register and where Controllers fail over

In a Site containing primary and satellite zones, with VDAs at minimum version 7.7:

  • A VDA in the primary zone registers with a Controller in the primary zone. A VDA in the primary zone will never attempt to register with a Controller in a satellite zone.
  • A VDA in a satellite zone registers with a local Controller, if possible. (This is considered the preferred Controller.)  If no local Controllers are available (for example, because the local Controllers cannot accept more VDA registrations or the local Controllers have failed), the VDA will attempt to register with a Controller in the primary zone. In this case, the VDA stays registered in the primary zone, even if a Controller in satellite zone becomes available again. A VDA in a satellite zone will never attempt to register with a Controller in another satellite zone.
  • When auto-update is enabled for VDA discovery of Controllers, and you specify a list of Controller addresses during VDA installation, a Controller is randomly selected from that list for initial registration (regardless of which zone the Controller resides in). After the machine with that VDA is restarted, the VDA will start to prefer registering with a Controller in its local zone.
  • If a Controller in a satellite zone fails, it fails over to another local Controller, if possible. If no local Controllers are available, it fails over to a Controller in the primary zone.
  • If you move a Controller in or out of a zone, and auto-update is enabled, VDAs in both zones receive updated lists indicating which Controllers are local and which are in the primary zone, so they know with whom they can register and accept connections from.
  • If you move a Machine Catalog to another zone, the VDAs in that catalog will re-register with Controllers in the zone where you moved the catalog. (When you move a catalog, make sure you also move any associated host connection to the same zone.)
  • Controllers in the primary zone keep connection leasing data for all zones. Controllers in satellite zones keep connection leasing data for their own zone and the primary zone, but not data for any other satellite zones.

For Sites containing VDA versions earlier than 7.7:

  • A VDA in a satellite zone will accept requests from Controllers in their local zone and the primary zone. (VDAs at minimum version 7.7 can accept Controller requests from other satellite zones.)
  • A VDA in a satellite zone will register with a Controller in the primary zone or the local zone at random. (VDAs at minimum version 7.7 prefer the local zone.)

Considerations, requirements, and best practice

  • You can place the following items in a zone: Controllers, Machine Catalogs, and host connections. If a Machine Catalog uses a host connection, both the catalog and the connection should be in the same zone. 
  • When you create a production Site and then create the first Machine Catalog and Delivery Group, all items are in the primary zone – you cannot create satellite zones until after you complete that initial setup.  (If you create an empty Site, the primary zone will initially contain only a Controller; you can create satellite zones before or after creating a Machine Catalog and Delivery Group.)
  • When you create the first satellite zone containing one or more items, all other items in your Site remain in the primary zone.
  • The primary zone is named 'Primary' by default; you can change that name. Although the Studio display indicates which zone is the primary zone, it is best practice to use an easily-identifiable name for the primary zone. You can reassign the primary zone (that is, make another zone the primary zone), but it should always contain the Site database and any high availability servers.
  • The Site database should always be in the primary zone.
  • After you create a zone, you can later move items from one zone to another. Note that this flexibility allows you to potentially separate items that work best in close proximity - for example, moving a Machine Catalog to a different zone than the connection (host) that creates the machines in the catalog, could affect performance. So, consider potential unintended effects before moving items between zones. Keep a catalog and the host connection it uses in the same zone.
  • For optimal performance, install Studio and Director only in the primary zone. If you want another Studio instance in a satellite zone (for example, if a satellite zone containing Controllers is being used as failover in the event the primary zone becomes inaccessible), run Studio as a locally-published application. You can also access Director from a satellite zone because it is a web application.
  • Ideally, NetScaler Gateway in a satellite zone should be used for user connections coming into that zone from other zones or external locations, although you can use it for connections within the zone.

Create and manage zones

A Full Administrator can perform all zone creation and management tasks. However, you can also create a custom role that allows you to create, edit, or delete a zone. Moving items between zones does not require zone-related permissions (except zone read permission); however, you must have edit permission for the items you are moving. For example, to move a Machine Catalog from one zone to another, you must have edit permission for that Machine Catalog. For more information, see the Delegated Administration article.

If you use Provisioning Services: The Provisioning Services console provided with this release is not aware of zones, so Citrix recommends using Studio to create Machine Catalogs that you want to place in satellite zones. Use the Studio wizard to create the catalog, specifying the correct satellite zone. Then, use the Provisioning Services console to provision machines in that catalog. (If you create the catalog using the Provisioning Services wizard, it will be placed in the primary zone, and you will need to use Studio to move it to the satellite zone later.)

Create a zone

  1. Select Configuration > Zones in the Studio navigation pane.
  2. Select Create Zone in the Actions pane.
  3. Enter a name for the zone, and a description (optional). The name must be unique within the Site.
  4. Select the items to place in the new zone. You can filter or search the list of items from which you can select. You can also create an empty zone; simply do not select any items.
  5. Click Save.

As an alternative to this method, you can select one or more items in Studio and then select Create Zone in the Actions pane.

Change a zone name or description

  1. Select Configuration > Zones in the Studio navigation pane.
  2. Select a zone and then select Edit Zone in the Actions pane.
  3. Change the zone name and/or description. If you change the name of the primary zone, make sure the zone remains easily identifiable as the primary zone.
  4. Click OK or Apply.

Move items from one zone to another zone

  1. Select Configuration > Zones in the Studio navigation pane.
  2. Select one or more items.
  3. Complete one of these actions: either drag the items to the destination zone, or select Move Items in the Actions pane and then specify which zone to move them to.

A confirmation message lists the items you selected and asks if you are sure you want to move all of them.

Remember: When a Machine Catalog uses a host connection to a hypervisor or cloud service, both the catalog and the connection should be in the same zone.  Otherwise, performance can be affected. If you move one, move the other, too.

Delete a zone

A zone must be empty before it can be deleted. You cannot delete the primary zone.

  1. Select Configuration > Zones in the Studio navigation pane.
  2. Select a zone.
  3. Select Delete Zone from the Actions pane. If the zone is not empty (it contains items), you are asked to choose the zone where those items will be moved.
  4. Confirm the deletion.

Other actions that include specifying zones

When you add a host connection or create a Machine Catalog (other than during Site creation), you can specify a zone where the item will be assigned, if you have already created at least one satellite zone.

In most cases, the primary zone is the default. When using Machine Creation Services to create a Machine Catalog, the zone that is configured for the host connection is automatically selected.

If the Site contains no satellite zones, the primary zone is assumed and the zone selection box does not appear.