Among built-in tools that reduce disk footprint in Windows 10, the compact command supports compressing OS files. Essentially it works because it compresses static OS executable files. These remain unchanged over time, unless replaced outright. Most modern CPUs can decompress data faster even than most SSDs can read it. This goes double for the eMMC (embedded MultiMedicaCard) devices found in inexpensive tablets and notebooks. Because these are typically 32 GB or smaller, they also benefit most from whatever space-saving techniques savvy admins use for Windows 10. In short, Win10 compact saves room on disk!
How Win10 Compact Saves Room Pays Off
A quick look at the command line reference info for the compact command shows most of its capabilities:
Key attributes for maximum space savings include /CompactOS and /EXE.
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The secrets for best results from this command come from compressing all OS binaries, using the /CompactOS:always directive. This makes the system state “Compact” and keeps things that way. The other key directive is /EXE, which can select a more compact compression algorithm than the default XPRESS4K value. Although it is fastest, it is also the least compressed of the options available. But smaller tablets and low-powered notebook PCs, especially those with eMMC storage, are slow. Thus, admins may need to experiment with other options for the best speed-space tradeoff. Users don’t like painfully slow systems, even if they do provide more storage space!
A January 5, 2017 Microsoft Developer Resources article entitled “Compact OS, single-instancing, and image optimization” goes into more detail on this subject. It also explains how DISM helps achieve maximum compaction and image optimization, for those who manage Windows images for deployment, or hardware devices that use them. Other techniques include Full Flash Updates (FFUs), or unattend.xml files with SysPrep. All in all, this is great stuff, especially for those who manage smaller and slower Windows 10 tablets or notebook PCs.