Failover (im)possibilities of XenDesktop 7.x Part 5: After the XenDesktop 7.11 release
- Published: Tuesday, 06 December 2016
In the earlier article series Failover (im)possibilities <<LINK to part 4>> I wrote about the failover/load balancing possibilities in XenDesktop 7.x, where 4 was about Desktop 7.9. In this article I will discuss the XenDesktop 7.11 release and will also go into a bit more detail what is expected in future releases (where possible).
Connection Leasing (formerly known in XenApp 6.5 as Local Host Cache)
As written in part 1 we already discussed the importance of the Citrix XenDesktop Site database in the XenDesktop/XenApp 7.6 and earlier released. In 7.6 Connection Leasing was introduced that partly fills in the current need for the well-known XenApp 6.5 Local Host Cache functionality.
In part 4 I mentioned the announcement made during one of the Citrix Synergy of the comeback of Local Host Cache (LHC) functionality in a future version of XenDesktop/XenApp 7.x. Probably many people expected that this functionality would be available in version 7.11. Unfortunate it is not in this release available. It can be that Citrix announced it really early that it will be become available, but was not intended to be released in the next version after Synergy. Secondly it can be that they aimed for release 7.11, but the code was not finished on time (they are developing using sprints). Or the last option is that the code is finished, but contains a bug or bugs which causes that the functionality is not released. For the LCH successor we need to have to wait at least for the next version.
Taking a look at the Connection Leasing part nothing has changed within this release. Which is logically as the functionality will be taken over by the LCH successor, so why would Citrix put effort into this functionality. Maybe the Connection Leasing functionality is the basis for the LCH successor, but also in this case it’s logical that there is no enhancements available in the XenDesktop 7.11 release.
As described StoreFront 3.5 offered the multi-site settings in the GUI. StoreFront 3.6 added the possibility to load balance using non-identical farms. StoreFront 3.7 does not offer new functionality based for failover or load balancing on the StoreFront functionality. StoreFront 3.7 is a requirement for new functionality within zones described later in this document. So you need to take that into account if you would like to use that new functionality.
In XenDesktop 7.8 de priority option was introduced in the GUI (PowerShell was available from 7.5), where with XenDesktop 7.9 this feature was embedded in the Application Groups where you could set the priority for a set of applications. In version 7.11 the priority and groups features are not adjusted. So the functionality is the same for applications, while the option is not available for Desktops. However Citrix added additional functionality to Zones that that offer similar options, which I will go into details in the next paragraph.
While that new functionality has overlap in functionality we can ask the question what will happen with the priority feature. It’s a different methodology, but can make configuration more complex if both techniques are used together. See for more details my article about Zones in XenDesktop 7.11.
Also on one of the session at Citrix Synergy 2016 Zone Preference was mentioned as a feature that will be brought back to XenDesktop as well. Citrix re-introduced this feature in XenDesktop 7.11.
In XenDesktop 7.7 zones could be uses to regulate the traffic between the VDAs (via a Machine Catalog assigned to a zone) and the Delivery Controller. Now the Zone Preference functionality is added to Zones component.
You can assign a user(s) and/or group(s) to a Zone. When a user logs on XenDesktop will check if the user is assigned to a zone and if so a session to a VDA will be set-up that is part of Machine Catalog which belongs to the same zone. If no VDAs in the zone are available the least busy VDA in the Delivery Group will be assigned. This behavior can be altered by setting that the user can connect to a VDA that belongs the Machine Catalog(s) available in the zone. The configuration is done on the Zone part in Citrix Studio.
Also for Published Applications this functionality is available. The user/group assignment can be used, but you can set specific settings for each Published Application as well. This application assignment overrules the user/group assignment, so you can make differentiations for specific applications. If no VDA is available to the zone, just as with a desktop another least busy VDA will be used. Also you can configure that only the VDAs available in the zone are allowed. For applications you can also configure that the user/group assignment should be ignored and all VDAs in the Delivery Group should be used. Configuration is best done within the Application Properties as the Zone component offers less options than within the application properties. It is possible to combine the Zone Preference with the Priority feature, where Zone Preference have the higher preference.
If comparison with earlier versions of XenApp we are missing the possibility to regulate the selection of a VDA when the configured zone does not have resources available. But probably the majority of the customers have enough to this enhancements to the product.
For more details about configuring and using the Zone Preference functionality, please check my other article Zones in XenDesktop 7.11.
Citrix Provisioning Services
With XenDesktop 7.11 also Citrix Provisioning Services 7.11 was released. Again no major changes to Provisioning Services. The current load balancing is sufficient for most of the use cases and therefore it’s logical that my thinking caps are still not high on the list of possible features. The only enhancement is based on the database connections supporting SQL Server Always On Failover infrastructure located over multi subnet environments.
In this additional fifth article in the series about Citrix XenDesktop Failover (im)possibilities I took a look what XenDesktop 7.11 brought us for failover possibilities. Summarized the enhancement is available in the Zone Preference functionality, which is a major achievement for Citrix. This was one of the functionality that kept several companies on XenApp 6.5 currently. Unfortunate we are missing the option to set an order within the zones for failover possibilities. But we are close to the functionality in earlier versions.
It’s a pity that the Local Host Cache functionality is still missing. Hopefully Citrix is adding this functionality in the next release. If that’s the case than we are getting really close that the so called feature gap is closed.