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New OS Compression in Windows 10

Over at this morning, I found a simply fascinating story about a new version of “OS compression” that’s making its debut in Windows 10. The ultimate source for this info is a March 16 Blogging Windows post entitled “How Windows 10 achieves its compact footprint.” So far, there’s nothing else about this on TechNet or others Windows technical sources, though does have a couple of threads that address the kinds of issues to which Mr. Thurrott refers when he indicates that smaller Windows 8.1 devices that use WIMBOOT (a different and older form of OS compression that requires a separate recovery partition on the system/boot storage device) must jump through some special hoops to upgrade from 8.1 to Windows 10 without encountering hiccups along the way.

The MS blog post indicates that Windows 10 “gives back approximately 1.5 GB of storage for 32-bit and 2.6 GB of storage for 64-bit Windows. Phones will also be able to use this same efficient compression algorithm and likewise have capacity savings with Windows 10.” In addition, the post explains that MS is “…redesigning Windows Refresh and Reset functionalities to no longer use a separate recovery image (often preinstalled by manufacturers today) in order to bring Windows devices back to a pristine state. This reduces Windows’ storage footprint further as the recovery image on typical devices can range in size from 4 GB to 12 GB, depending on the make and model.” Here’s a pie chart from the blog post that’s entitled “Example Savings on 64-bit Windows:”

On a 32 GB set-up (typical for low-end tablets and many phones) 6.6 GB of savings is significant.

The post goes on further to explain that compression is selective and is intended not to “adversely affect system responsiveness.” Factors considering when assessing compression include: amount of RAM available (which determines how often files must be retrieved from storage), and speed at which the device’s CPU can run the compression algorithm. By studying Windows 8 system compression and related performance, MS claims it has improved overall behavior and efficiency in Windows 10. It should be interesting to learn more about how things work — especially installation, reset and recovery — and to see what MS does to address “bringing upgrade to low capacity devices.” Good stuff! Now, if Mark Russinovich (or somebody on his team) will only dig into this in depth for the next edition of Windows Internals, and MS will publish some info about this on TechNet, we’ll all probably understand it a whole lot better…