August 7, 2013 | Written by: Andreas Groth
Share this post:
IBM has published several “virtual desktop” reference architectures. These articles will help you to explain the concept of stateless desktops to a less technical audience. More related articles are published by Andy here.
The inconsistency of today’s virtual desktop infrastructure terminology creates a lot of confusion, and that includes the description of the relationship between the user and the desktop image. Stateless desktops are often also referred to as non-persistent, pooled and dynamic and dedicated desktops as persistent or private. The image deployment model has a fundamental impact on the arguably most important metric for VDI — cost per user — so getting your point across to even the potentially less technical folks is imperative.
A stateless desktop is to the IT Administrator what a hotel room is to a property manager.
A property manager (IT administrator) has been tasked to provide and maintain accommodation (virtual desktops) on a tight budget to a large number of tenants (VDI users). He knows that unless housing is considered functional and homely by the tenants (user experience) the project will be considered a failure. He evaluates two approaches:
- Hotel (stateless desktops)
- Residential area with private properties (dedicated desktops)
1. The hotel (stateless desktop)
The tenant checks into the hotel and gets any available room (desktop), typically bringing their suitcase (user profile) that they use to customize the room with personal things while using it. They use it for a period of time, and will check out when it is not needed, removing all personal belongings.. The room will be cleaned (reset) so that the next tenant finds it “as new” (changes to the desktop will be discarded; making the desktop itself “stateless”). It will then be made available to any other potential tenant. The next time our tenant checks into the hotel he or she will most likely get a totally different apartment (desktop) but that isn’t an issue as long as it provides the same functionality.
The hotel’s tenants’ (users’) view:
- The room as functional and equipped with all the facilities and appliances they need (Microsoft Office, mail applications).
- They are able to adequately personalize the space, depending on how big of a suitcase they bring (user profile).
- The hotel chain would provide centralized storage for permanent personal items outside your hotel (network drives, folder redirection). Some even provide the equivalent of a personal designer service that allows for advanced customization of your room to make it really feel like yours (advanced profile management software like AppSense or RES).
- The hotel will obviously not allow you to buy a personal home cinema system (your favourite PC game) and permanently install it in the hotel apartment. The hotel could, however, provide custom services (applications) through alternative methods if required. Think of it as room service (application streaming or XenApp publishing).
The property manager’s view (IT administrator):
- There is a low build and maintenance effort. The rooms are from a common blueprint (golden image) and have a common set of furniture and appliances (apps). Custom services cost extra but can be handled (streaming apps).
- Availability requirements are also low. If a room is unavailable due to scheduled maintainance or unforeseen problems (think of a flooded bathroom as the equivalent of a corrupted image) the tenant can use another apartment (connect to another desktop). There is no dependency between the tenant and room (user and desktop image). Even if the entire hotel experiences a power cut (host failure) with all rooms becoming unusable, the tenant can simply check into another hotel as long as total capacity across all hotels is sufficient.
So, the stateless desktop provides the user with a set of common capabilities and applications, a mechanism to personalize, use and store personal data permanently that is accessible from any desktop but natively does not allow you to install personal applications into the image. You will never own the desktop but the user experience is close to that of a privately owned one, giving a suitable experience for most users. The stateless desktop allows the administrator to build desktops from a common image base that is easily deployed and maintained, the stateless desktop itself does not need to be made highly available and can easily be replaced with another available desktop if the desktop (or host) becomes unavailable.
In my next post, we’ll discuss how dedicated desktops are like private property.