XenDesktop 7.6: 3 New Features; 2 Good, 1 Doesn’t Matter

On 13 January 2015 by Pete Petersen
XenDesktop 7.6

Image sources: https://www.pinterest.com/pin/433190057881482002/ http://forums.nexusmods.com/


As part of the XenDesktop/XenApp 7.6 release, Citrix has introduced several new features. Three of them will be focused on here.

  • Connection Leasing
  • Session Prelaunch and Session Lingering
  • IMA Support for Director

Connection Leasing

Let’s start this discussion with some text from Citrix:

To ensure that the XenApp site database is always available, Citrix recommends starting with a fault-tolerant Microsoft SQL Server deployment by following high availability best practices from Microsoft. However, network issues and interruptions may prevent Delivery Controllers from accessing the database, resulting in users not being able to connect to their applications or desktop.
The Connection Leasing feature supplements the SQL Server high availability best practices by enabling users to connect and reconnect to their most recently used applications and desktops, even when the XenApp site database is not available.
When you enable connection leasing, each Delivery Controller caches user connections to applications and desktops during normal operations (when the database is available). If the database becomes unavailable, the Delivery Controller enters Leased Connection mode and “replays” the cached operations when a user attempts to connect or reconnect to a recently used application or desktop from StoreFront.

This means that although recent resources are cached, all available resources are not. In the event of a site database loss, users would be able to launch the resources that are cached, but other resources would be unavailable until the site database returned.

The cached information is good for two weeks by default, in both directions. This means that if a user launched an application a week and a half ago, and the database is lost, the user can launch the application from cache for another half a week until that two-week lease expires. It is definitely not Local Host Cache.

Disconnected (not logged off) applications do not expire while in that state. It is also not available for pooled VDI desktops. It is, however, supported for server-hosted applications and desktops, and statically-assigned desktops. Connection Leasing is also available by default.

Connection Leasing is really only meant to cover a network interruption or other temporary DB connection failure, rather than as in the case of XA6.5, LHC could cover everything.

Session Prelaunch and Session Lingering

Prelaunching a session means that as a user logs into Receiver, a connection is automatically made to a XenApp resource. This is good because the connection penalty is paid at login time where the user expects it rather than at app launch time when they actually are expecting the app to appear quickly.

While Linger is available for all Receiver versions, Prelaunch will only work with Windows Receivers and requires a registry entry on the local client device: HKLM\software\wow6432node\citrix\dazzle and change the EnablePreLaunch value from blank to “True”

In addition, sometimes Linger takes longer than specified to clear the idle session.

This is a much-needed and very welcome addition to Citrix’s bread and butter product.

IMA Support for Director

Citrix has brought back IMA support for Director in XD/XA7.6. This means that you can now troubleshoot a XA6.5 environment with Director 7.6. Although this seems simplistic, imagine assigning a help desk the task of looking after both XenApp 7.6 and XenApp 6.5 users. The help desk techs can now go to one console (Director) to administer both, and have, in many cases, much more ready and detailed information available in a more intuitive interface.

In the End

Ultimately, the view is that Session Prelaunch and Session Lingering, along with IMA Support for Director are very welcome additions to the XenDesktop experience. Connection Leasing seems to be a half-hearted attempt at getting us somewhere back in the neighborhood of Local Host Cache, but at this point does not fit the bill.

Update! – 27 Apr 2016

In the course of the past 16 Months since XD 7.6 has been released, it has become clear that 7.6 is the stable version, as XenApp 6.5 and XenDesktop 5.6 were to their respective feature sets. Feature Pack 3 added the needed Framehawk technology for low bandwidth / high latency connections, among other things, and XenDesktop 7.7 and 7.8 have integrated those needed features into the ISO install.

With the integrations and added features, there is little reason to delay working toward XenDesktop/XenApp 7.8, and with Citrix’s more recent update approach, keeping up should be less of a hassle than it used to be.