Windows as a service is the approach Microsoft introduced with Windows 10 to deploy, update and service the operating system.
Instead of releasing a new version of Windows every three to five years, as the company did with past iterations of the operating system, Microsoft will continually update Windows 10. The updates are categorized in two ways: feature updates and quality updates.
Feature updates occur about twice a year, roughly scheduled for March and September. They contain new functionalities for the operating system (OS). Quality updates are cumulative updates that come out at least once a month and contain security patches and other fixes to make the OS more reliable. Because they are cumulative, the latest update carries all of the updates that came before it and trumps any previous updates. Each feature update continues to receive quality updates for 18 months after its initial release.
IT professionals can use the three servicing channels within Windows as a service to create deployment groups with different users or devices that they deliver the updates to at different cadences. The three servicing channels are:
Windows Insider Program: Members of the Windows Insider Program get access to whatever updates are coming as soon as they are available during Microsoft's development process. This allows IT to work with the updates and test compatibility before the update goes out to the general public. In addition, Microsoft encourages members of the Windows Insider Program to provide feedback on any issues they encounter. The gestation period for updates is about four months, but it depends on the feedback Microsoft receives from Insider members. When an update is ready for general use -- meaning customers, independent software vendors and Microsoft partners consider it functional -- Microsoft declares it to be "ready for broad deployment."
Semi-Annual Channel: This channel follows the twice-per-year update model. It was formerly known as the Current Branch for Business. Organizations can defer updates for up to one year with the Semi-Annual Channel if they have Windows Server Update Services (WSUS), Microsoft System Center Configuration Manager (SCCM) or Windows Update for Business. The Semi-Annual Channel has two subsets: Targeted, which is similar to what Current Branch was, and Broad, which is similar to what Current Branch for Business was. With Targeted, IT should test the update on more advanced devices with the latest chipsets and capabilities. If the tests are positive, then the update becomes Broad and IT can distribute it throughout the organization.
Long-Term Servicing Channel (LTSC): This channel is designed for specialized devices such as ATMs where security and stability are paramount and the downtime associated with OS updates is unacceptable. The LTSC, available only for the Windows 10 Enterprise Long-Term Servicing Branch edition of the OS, blocks feature updates but allows quality updates to continue. IT can defer the quality updates using Windows Update, Windows Update for Business, WSUS or SCCM. Updates in the LTSC occur about once every three years, and IT can implement them through in-place upgrades.
LTSC retains update support for a decade. The first five years maintain standard support, while the second five years get extended support.
IT can use many of the same management tools it used in previous versions of Windows to control updates, including:
Windows Update: With Windows Update, IT can pick and choose which devices are part of the Semi-Annual Channel and which devices within that channel can defer updates.
Windows Update for Business: In addition to deciding which devices defer updates, Windows Update for Business allows IT to centrally manage updates through Group Policy. IT can defer updates with Windows Update for Business for up to one full year. Windows Update for Business is also available in the cloud with Microsoft Intune.
WSUS: WSUS takes IT professionals' deferment powers a step further by allowing them to approve when the update goes to different specific devices or groups of devices.
SCCM: SCCM allows IT to defer and approve updates, as well as target specific devices or groups of devices and manage how much bandwidth the Windows update consumes and when the update runs.
Windows as a service in the past
Prior to Windows 10, Windows as a service referred to a delivery method for Windows virtual desktops and applications through a cloud service provider.
In that model, the service provider managed the back-end responsibilities of data storage, backup, security, patches and upgrades. It copied the customer's personal data to and from the virtual desktop during logon and logoff. Similar to Desktop as a Service, IT purchased Windows as a service on a subscription basis. According to Microsoft's virtualization licensing policy, the end user was required to hold valid license keys for each Microsoft product IT pushed to his virtual desktop.