Thin client vendors would have you believe that doing virtual desktop infrastructure without thin client devices is some kind of recklessness. The reality is that a large proportion of such deployments use PCs for virtual desktop access -- or even mobile devices.
The flexibility of accessing a virtual desktop using whatever device is in front of a user is a huge plus for virtual desktop infrastructure (VDI) over conventional desktops. The good news is that most non-thin-client access uses exactly the same mechanisms as thin clients, so support often involves simply making the client software available and making sure your staff know what is possible.
Reusing existing PCs
Many organizations choose not to use thin clients and instead reuse the PCs that they already have. If you decide to use old PCs to host your VDI, whether those PCs are new or old, inside or outside the firewall, they are still not thin clients. While the hardware may not be up to the job of running Windows 7 (or 8), the old PC may well be up to the job of running a modern remote display protocol. It doesn't take too much reconfiguration to make an old PC behave like a thin client device -- opening the VDI session automatically and providing seamless desktop access.
One of the nice things is that you probably already have an infrastructure in place to manage these PCs; you should be able to use the same tool to make the PC into a VDI client without visiting very single one. This can be a useful way of moving the thin client expense out into the second year of the VDI deployment. Just make sure to replace the old PCs before their hard drives, fans or power supplies start to fail. The downside of reusing PCs is the continuing requirement to manage their operating system and antivirus updates. Reusing existing PCs purely for VDI access is usually a transition phase, even if the phase lasts for years.
Another reason to have long-term access from a PC is when that PC has some other role in addition to being a VDI client. For example, I've seen a VDI deployed to enable a business partner's staff to access applications without the data leaving the company data center. This was for a financial services company allowing external brokers access to their custom-developed systems. A VDI enabled secure access from the broker's own PC to a tightly managed desktop. Access can be strictly controlled by the VDI operator, but no infrastructure needs to be provided to the broker's site.
More on thin client devices
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Making sure your thin client vendor sticks around
Thin client choice should depend on manageability
Getting to know mobile thin clients
The same method is a great way to allow external IT and business support teams access to your organization's network. Users from outside the company can sit in their own offices and use their PC to access a virtual desktop, usually over the Internet. This is much more secure than allowing access via a virtual private network (VPN) from the outside offices, and much cheaper than providing dedicated WAN circuits to your partner organization's offices. Partner staff can also be more productive, because switching in and out of a virtual desktop is much quicker than opening a VPN connection.
Another way for the PC to have a role in VDI is when you're allowing staff to work from home or wherever they find themselves. Whether it's home PCs, a hot desk at a remote office, a friend's house, airline lounge or an Internet café, there are a lot of places where the device in front of your staff will not be a thin client. Again, the simplicity of access using VDI is a huge win over older methods that involved company laptops and VPNs.
Mobile instead of thin
Mobile devices are an increasing part of the IT landscape. One reason for deploying VDI is to enable bring your own device, or BYOD), where staff are given a budget to provide a compute device of their choice. Corporate applications can be provided to a strictly controlled virtual desktop, while employees are allowed to make their own choice of the device they use to access that desktop. This allows them to buy Apple laptops or Android tablets or whatever else expresses their personality, yet access to the compute environment is controlled by IT. I doubt any employee would buy a thin client, because they want to make use of the device after the workday is over.
Led by the march of the iDevice, many people now carry a device with a VDI client in their pocket every day. This anytime access to a desktop exemplifies the agility and adaptability of VDI -- a full-featured application set using whatever device you choose from wherever you happen to be.
Limiting your VDI deployment to thin client devices and your offices will reduce the value of VDI in most environments. Enable your users to access their virtual desktop from multiple devices for different moments.