Desktop Virtualization › Managing the Virtual Desktops from CA ITCM › Implementation Guidelines for Virtual Desktops

Implementation Guidelines for Virtual Desktops

For software packages that are installed to individual virtual desktops rather than to the golden template, you must consider the following limitations and guidelines:

• Packages that are not staged in the software library of the scalability server to which the agent is registered are not reinstalled.
• Reinstall is not supported for added procedures with new files.
• Reinstall is not supported for the User Profiles agent, only the Computer agent.
• When a virtual desktop is checked out using VMware View's Offline Desktop feature and rolled back (that is, checkout is discarded), any changes to the software state remain in the instance software database. When Offline RAC is performed, the software is reinstalled because it was recorded in the state database and not removed during rollback. Therefore, the software must be uninstalled manually if you do not want it.
• Sending software delivery jobs with reboot/logoff/shutdown options enabled is not supported for nonpersistent virtual desktops. A nonpersistent desktop is tied to a user only for as long as the user is logged on. The next time the user logs on, the user can be allocated to a different desktop. Hence, these options are not logical for this case.
• Packages that take a long time to transfer over the network or that take a long time to install must be installed to the golden template rather than to the individual virtual desktop. If not, the reinstallation time becomes unacceptable.
• Virtualized applications can be pre-staged on the golden template and later provisioned to individual virtual desktops using standalone installation. This way your network bandwidth usage is minimized during recompose/refresh and during use.
• A result similar to the previous item can be achieved using managed package formats like SXP, PIF and MSI with some research and possibly some tweaking. For example, SXP provides a user filter that allows the package to be installed to the golden template. However, the filter is only made available to users of the clones that belong to specific local or active directory user groups.
• Virtualized applications must be provisioned to individual virtual desktops in streaming mode. This way network bandwidth usage can be minimized during recompose/refresh, but not during use.
• Applications that store their configuration outside of the redirected user profile/folders do not automatically preserve their configuration after reinstall. Applications that reset their configuration rather than inheriting it as part of install also suffer from this issue.
• If both the template software state database and the instance software state database contain records of the same software but of different versions, the upgrade or downgrade is still performed by the Offline RAC. The administrator is responsible for configuring the system accordingly and preventing such a case, especially in downgrade scenarios.
• DTS download method is not supported for the virtual desktop agent.
• For nonpersistent desktop pools, reinstallations are only done when a user logs on. When the user logs off a cloned desktop that is part of a nonpersistent desktop pool created with the "Power off and delete virtual machine after first use" option selected in VMware View 4.0, then the cloned desktop is in the Locked by RAC state until a user logs on again. For VMware View 4.5, the equivalent situation occurs when the "Delete or refresh desktop on logoff" option is set to "Refresh Immediately" or "Delete Immediately." Therefore, we recommend that any critical patches be deployed as part of the golden template instead of deploying them as a part of the clone.
• We recommend that you disable the user profile mode for software delivery functionality in the case of linked clone virtual desktops.

  User profiles are not needed here because there is a one-to-one relationship between the user and the virtual desktop. Enablement of user profiles causes additional communication between the agent and scalability server, which can affect overall scalability.