According to market analyst company, The 451 Group, the market for virtualised desktop environments (VDI) is estimated to reach $5.6billion by next year. With the ability to provide high performance desktop images for around £50 – £100 per user, it’s no surprise that we’re seeing more and more customers extending their virtualised environments to the desktop.Virtualising a desktop makes a lot of sense for enterprises. The ability to move a user’s physical desktop within the data centre means gaining control centrally for the management and maintenance of those desktops. The user is provided with remote access to their virtual machine, which often provides an improved user experience as well.An attractive proposition for many IT departments, VDI enables the IT department to make changes – whether that’s patching, updates, security amendments and so on – to a single ‘gold’ desktop image and distribute it to all users. It simplifies security since the data is no longer held on the desktop, laptop or mobile device – rather it’s stored, managed and secured in the data centre. Performance can also be improved significantly with processing power increased more efficiently centrally than spread thinly locally.While the benefits of hosted desktops are widely understood, one area that is causing confusion is the difference between persistent and non persistent desktops and when to use them. In fact the issue is not as complex as many believe – it is as simple as clearly understanding your environment and defining how your users work. Once you have this knowledge you can apply it to identify whether you need to create a persistent or non persistent environment.So what is the difference between the two approaches? They can be easily defined:Persistent virtual desktops – having your users access to a permanent session even when logged off ensuring that you have licences and – more importantly sufficient capacity and performance for them to do so.Non persistent virtual desktops – a desktop is only provided as long as the user is logged on as it is shut down once the session is over.Persistent VDI is also known as one-to-one – so you have one virtual desktop to one user, whereas non persistent means having one virtual desktop to many users. In a persistent environment that means that changes made by the user, for example downloading a new app or shortcut to where a document is saved, remains in place and is shown the next time they log on. Within a one-to-many environment this isn’t so. The benefit of both is obvious. With a persistent environment users gain a more permanent experience but user licensing costs and the storage required to host each desktop is greater, whereas non persistent environments are usually 30% cheaper but less like a desktop or PC experience.So which one is right for your company? Typically if your users need to have a permanent session that caters significant changes over a period of days that need to be recorded e.g. developers, data analysts and so on, a persistent environment would be better, but if they don’t need to adapt or personalise the desktop, e.g call centre or retail staff then a non persistent approach is likely to be more cost effective. The good news is that this isn’t an ‘either/or’ scenario, you can mix it up and have a combination of both environments at different points of the day or for different users. The key to a successful deployment is really understanding how and why your users do what they do every day and building the deployment around them.