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Windows Server 2025 gains native NVMe support, 14 years after its introduction — groundbreaking I/O stack drops SCSI emulation limitations for massive throughput and CPU efficiency gains
There's pretty big news for Windows Server administrators. After some delays, starting with Windows Server 2025 and its latest October Cumulative update, the operating system will finally support native NVMe I/O, marking the end of an era where requests were translated to SCSI bus commands, even with the highest-powered drives.
The feature has now reached General Availability and is built right into the OS, though it's not enabled by default. Sysadmins willing to take the plunge only have to tweak a registry key, or add a group policy MSI, and they can enjoy up to 80% higher IOPS and up to 45% lower CPU utilization under a high I/O load. This should be a shot in the arm for scenarios involving high-performance file serving, virtualization, AI and ML workloads, and databases.
(Image credit: Microsoft)
Those figures came from a single test setup that though powerful, didn't even seem particularly exotic for this arena: a two-socket Intel system with 208 logical cores, 128 GB of RAM, and a Solidigm D7-PS1010 3.5TB PCIe 5.0 solid-state drive. Even with a single I/O thread, the system saw gains of 45% IOPS, increasing to 78% at eight threads, and 71% at 16 threads. Meanwhile, CPU load under 4K random reads saw a 41% reduction with eight threads and 47% with 16.
Microsoft's engineering team claims that "the whole I/O processing workflow is redesigned for extreme performance." Besides the raw performance gains, the improvements to the I/O locking mechanism should result in lower latency and round-trip times overall.
(Image credit: Microsoft)
A thread on Reddit contains some interesting comments from anecdotal tests; some claim they saw no difference in their systems, while others hypothesized that only PCIe 5.0 NVMe devices could really make a significant use of the improved I/O stack. As for consumer-grade drives, one tester actually saw reduced performance with a Western Digital SSD, suggesting that some drives may be tuned to the old way of doing things.
There's no word on when this feature will arrive in plain Windows 11. Given the varying quality of consumer drives' firmware, there will probably be a lot of testing involved to bring the new I/O stack to home PCs, and it's equally likely that it'll be enabled or disabled depending on the drive in question.
Although common home computing scenarios don't have much to gain from added I/O, there might be tangible gains in a few specific areas. First, the redesigned I/O locking mechanism may result in a smoother overall experience, with fewer instances where a single application slamming the drive still brings system responsiveness to a halt — or when multiple tasks are occurring simultaneously, such as at the end of the Windows boot process, when always-on applications are starting. Game times can also see a reduction given the lower CPU load, and DirectStorage might see renewed interest for the same reason. We'll be sure to test all of this when the time comes.
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Bruno Ferreira is a contributing writer for Tom's Hardware. He has decades of experience with PC hardware and assorted sundries, alongside a career as a developer. He's obsessed with detail and has a tendency to ramble on the topics he loves. When not doing that, he's usually playing games, or at live music shows and festivals.
I don't see what so groundbreaking. Most companies using this kind of storage is using linux or hosted environment while running windows in a virtual machine.
