The adoption of new technologies such as desktop virtualization (e.g. Citrix® XenDesktop®, VMware® Horizon View™) has radically changed the desktop landscape making software license compliance and license optimization even more difficult. The challenge of tracking application installation and usage in this environment combined with ever changing, complex or undocumented product use rights puts organizations at risk of being noncompliant. The difficulty of getting inventory data will be examined below. Virtual desktop licensing rules— mainly for Microsoft, will also be described in this paper.
For many years, desktop virtualization (aka Virtual Desktop Infrastructure (VDI)) has been positioned as a technology that will revolutionize the desktop market; many analysts predicted it would soon take over a significant share of the market. A significant percentage (see chart below) of medium to large organizations is currently in the process or has implemented virtual desktops but its use is restricted to a few case scenarios due to the heavy upfront investment required and the lack of significant return on investment.
As of today, desktop virtualization represents only a few percent of all desktops. However, it is still seen as one of the leading technologies that should take a more significant portion of the market in the coming years. One of the drivers fueling these forecasts is the rapid adoption of mobile devices and Bring Your Own Device (BYOD) policies by organizations. For these devices, the virtual desktop offers end users the flexibility to access their business environment from anywhere, at any time, from almost any device, running any operating system.
Drivers for Desktop Virtualization
(Organizations rating benefits of desktop virtualization "quite or very important")
Percentages based on a 4 or 5 rating on a scale of 1 to 5, where 5 is "very important."
|To centralize and simplify desktop management||86.2%|
|To improve security by maintaining and backing up data centrally||74.8%|
|To simplify and accelerate provisioning new desktops||74.2%|
|To lower infrastructure costs in power usage and/or hardware acquisition||73.0%|
|To provide end users with a convenient way to access their desktop environments remotely||67.5%|
|To extend refresh cycles for desktop PCs||65.7%|
|To reduce downtime caused by server/client hardware failure||62.7%|
Base: 300 respondents who have implemented, are piloting or planning to roll out desktop virtualization in the next year. Data: TechWeb survey of 490 IT decision makers.
The drivers for desktop virtualization, as shown in Figure 2, also include providing the ability for IT to centralize and simplify desktop management and accelerate provisioning of new desktops. In addition, this technology meets most organizations' security, compliance and regulatory requirements as data and applications are kept securely in the datacenter.
Types of Virtual Desktops
Virtual desktops come in two flavors: persistent and session based (or non-persistent). A persistent virtual machine is a virtual machine that is kept on a disk in the datacenter. Each time the user logs in, the previous session on that virtual machine is resumed. A user can create shortcuts, customize or install additional applications on his or her virtual desktop and all of these changes will be available in future sessions. Persistent virtual machines are usually only assigned to power users or administrators as they consume a large amount of resources—such as storage, in the datacenter.
The most common virtual desktops are session based. A session based virtual machine is assigned from a pool of virtual machines to the end user at log in time and wiped out each time the user logs out. Some vendors offer technical solutions to keep user changes across sessions and can even add applications to the virtual desktop template based on the user profile. In these instances, when the user logs in, the user personalization is added to the virtual desktop template.
Collecting Virtual Desktop Inventory
In the traditional desktop world, inventory is performed by an agent running within the operating system. Inventory consists of capturing software package data, for instance in Windows environments—from Programs and Features, file data, including contents of specific files, Windows registry or ISO 19770-2 tags. From there, data scrubbing and analysis is performed by an application recognition tool to generate the list of commercial products requiring a license. Additionally, a review of the login history on the device provides clues about its primary user. Typical inventory tools run on a schedule or are executed at log on time. Scheduling is the most commonly used strategy as it is less intrusive: it does not slow down the execution of the operating system when the end user requests access to it. It takes a few minutes for an inventory tool to capture data, the most resource intensive task being to perform a disk scan for executables, dlls, ISO 19770-2 tags or specific files.
For persistent virtual desktops, inventory tools are able to capture inventory and usage data the same way as for traditional desktops. On the other hand, session based virtual desktops are challenging for many reasons: there is no practical way to run the inventory on a schedule as the machine is wiped out every time the user logs out and this may happen multiple times a day. The lifespan of a virtual desktop can be extremely short, not leaving enough time for a scheduled or session triggered inventory to complete successfully. Inventory tools identify operating system instances by using various techniques: from analyzing key hardware or software properties (serial number, MAC address, IP address…) or by assigning a unique identifier to each one. A session based virtual desktop gets reused across multiple users or is re-imaged after use. So, it's difficult to get a unique inventory for each session. This can result in an ever growing, large number of devices that will need to be reconciled. An alternative approach is to set-up a mechanism to group sessions together on a per user basis.