There are plenty of reasons to use DaaS vs. VDI -- lower upfront costs, reduced IT maintenance, anytime user access...
-- but there are also benefits to VDI that make it a great choice for some organizations' desktop infrastructure. How do you know when to use each approach?
With DaaS, you can buy new desktops from a provider on short notice, and then surrender those desktops back, which is one of the huge benefits. You pay only for the desktops you choose to use each month, which makes it ideal for organizations that have surges in their desktop needs. Rather than having a large amount of equipment that you only use occasionally, you can use DaaS to deliver on short-term or seasonal desktop requirements.
Additionally, you can spin up cloud-based desktops for workers to use as part of your disaster recovery plan. This gives users much more flexibility in terms of where they can work and what devices they can use to access their desktops.
When to do DaaS vs VDI
If your shop wants to do VDI but lacks the in-house expertise to build and operate a complex VDI environment, then you are good potential DaaS customer, too. Instead of building an inadequate VDI platform and not having the experience to operate it, you could rent desktops from a DaaS provider. If you choose to do DaaS, your on-site desktop infrastructure could be as simple as a few thin clients, a print server and an Internet connection, particularly if you build a full server infrastructure with your DaaS provider.
Another good use for DaaS is if you expect a lot of growth in desktop use that will be spread over time. Your DaaS footprint can grow a little every month, but to grow with VDI, you need to plan for your maximum size right from the start. That means you either buy huge excess upfront, or regularly -- and disruptively -- upgrade hardware to add capacity to your VDI environment. Either way, with VDI, you have to pay for capacity well before you use it.
If you've moved your entire server infrastructure into a cloud provider's data center, you could benefit from also moving desktops to the same cloud provider. Keeping the desktops near the servers helps with application performance since it minimizes network latency. This is an even bigger driver if you use a community cloud.
Community clouds provide services to a specific set of customers, such as financial services firms or government contractors. In these cases, the community might have specific regulatory compliance requirements that the cloud provider meets. These same specialized requirements will likely apply to the desktops, so placing them in the community cloud is logical.
Why use VDI instead of DaaS?
The choice to use on-premises VDI is usually about scale, control or diversity. If you need to deliver 10,000 desktops, then you have the scale of a DaaS provider. At that scale, you can afford to design, deploy and optimize the virtual infrastructure just like a service provider. If you can achieve most of the economies of scale, then you can probably provide more cost-effective desktops internally, rather than having an external provider dedicate entire rows of racks to your desktops.
Control has always been an impediment to cloud adoption. Legal requirements in some jurisdictions about data sovereignty can make cloud services unworkable for companies in certain industries. When an organization must comply with multiple sets of regulations, rather than just one, it can be hard to find a DaaS platform that satisfies all requirements.
One characteristic of cloud services is they come in predefined configurations. Usually, you cannot special-order a custom DaaS desktop configuration; you simply choose from a menu. By contrast, VDI allows for a lot of customization, from different CPU, RAM and disk configurations, all the way to the ability to deliver rack workstations to users.
Stacking a lot of virtual machines (VMs) on a single virtualization host may not be suitable for many Windows PC use cases, and DaaS does not usually support these. If you need to buy a workstation at three to 10 times the cost of a standard PC, using a VM in its place probably won't give users the performance they need.
VDI usually allows a dedicated physical workstation or a customized VM for users who need high-end hardware, and it still keeps their desktops in the data center and allows for mobility. Specialist DaaS providers may be able to deliver this sort of capability, but it doesn't match the DaaS economies of scale model so well.
Maybe use both -- or neither
There will definitely be shops that choose DaaS for some workloads and build VDI for others. VDI might suit an enterprise desktop infrastructure with thousands of permanent staffers. That same organization might have seasonal workers who they use DaaS to accommodate.
And there might be parts of your business that need to access a specialist DaaS environment for regulatory or technology reasons. In truly global organizations, there is huge diversity, and mandating one technology to serve all requirements is a recipe for disaster.
One emerging trend is to have VDI products that support brokering connections to DaaS products as well as on-premises VDI. Having one access methodology to reach VDI and DaaS simplifies support. In some ways, this makes the DaaS provider just another data center in the desktop environment.
The elephant in the room in the discussion about DaaS vs. VDI is the option to do neither. Putting a PC on a user's desk isn't exciting or modern, but it does run Windows applications for that worker. Many companies will find that the sensible course of action is to keep doing what they did before, buying new PCs and installing applications on those desktops.
On the other hand, if you need benefits such as agility and flexibility that both VDI and DaaS provide, then you should consider one or both technologies.