Windows 25H2 makes 32 bytes offset after upgrade?

• Background: On Windows 11 23H2 in 2024 my Corsair NVMe drive ran stable. Later that year, the drive suddenly failed with BSOD and died eventually , and I suspect heat was the cause, since most motherboards place the NVMe socket close to the GPU with poor airflow. I relocated my new NVMe drive using an extension cable near a case fan, which lowered temps significantly.
• Performance and alignment: I discovered that partition alignment (especially on the C: system drive) is critical for SDD/NVMe performance. With proper 4K alignment I achieved full speed and lower temps.
• Windows 11 24H2/25H2: After upgrading to 24H2 this year I experienced (not related to this topic) instability. On 25H2 upgrade things improved overall, but I noticed that partition alignment had changed from 4096 to 32‑byte after the 25H2 upgrade ! With the new misalignment at 32‑byte offset the performance dropped and temps rose by 4–5 °C. This caused poor performance and higher temps. After manually restoring 4K alignment, everything returned to normal.
• Suspicion: I suspect that Windows 11 feature updates may alter partition alignment on the system drive(Microsoft standard of 32 byte and 1K byte. This could be dangerous for NVMe drives, since misalignment forces the controller to work harder, increases heat, and may shorten lifespan.

Questions for the community​

• Has anyone else seen partition alignment change after Windows updates?
• Could this be related to the known SSD/NVMe issues in 24H2 also?
• Is there a way to automatically verify or enforce alignment after major updates?
• Using msinfo32:
  1. Press Win + R, type msinfo32, press Enter.
  2. Go to Components → Storage → Disks.
  3. Look at “Partition Starting Offset.” Divide this number by 4096.
     • If the result is an integer, the partition is correctly aligned.
     • Example: 1,048,576 ÷ 4096 = 256 → aligned.
     • Example: 32 ÷ 4096 = 0.0078 → misaligned.

LBN1405 said:

Possible Link Between Windows 11 24H2/25H2 and Changed NVMe Partition Alignment ?

I’d like to share an experience that I haven’t seen documented elsewhere, but which may be relevant for anyone running newer SSD/NVMe drives on Windows 11.

• Background: On Windows 11 23H2 in 2024 my Corsair NVMe drive ran stable. Later that year, the drive suddenly failed with BSOD and died eventually , and I suspect heat was the cause, since most motherboards place the NVMe socket close to the GPU with poor airflow. I relocated my new NVMe drive using an extension cable near a case fan, which lowered temps significantly.
• Performance and alignment: I discovered that partition alignment (especially on the C: system drive) is critical for SDD/NVMe performance. With proper 4K alignment I achieved full speed and lower temps.
• Windows 11 24H2/25H2: After upgrading to 24H2 this year I experienced (not related to this topic) instability. On 25H2 upgrade things improved overall, but I noticed that partition alignment had changed from 4096 to 32‑byte after the 25H2 upgrade ! With the new misalignment at 32‑byte offset the performance dropped and temps rose by 4–5 °C. This caused poor performance and higher temps. After manually restoring 4K alignment, everything returned to normal.
• Suspicion: I suspect that Windows 11 feature updates may alter partition alignment on the system drive(Microsoft standard of 32 byte and 1K byte. This could be dangerous for NVMe drives, since misalignment forces the controller to work harder, increases heat, and may shorten lifespan.

Questions for the community​

• Has anyone else seen partition alignment change after Windows updates?
• Could this be related to the known SSD/NVMe issues in 24H2 also?
• Is there a way to automatically verify or enforce alignment after major updates?
• Using msinfo32:
  1. Press Win + R, type msinfo32, press Enter.
  2. Go to Components → Storage → Disks.
  3. Look at “Partition Starting Offset.” Divide this number by 4096.
     • If the result is an integer, the partition is correctly aligned.
     • Example: 1,048,576 ÷ 4096 = 256 → aligned.
     • Example: 32 ÷ 4096 = 0.0078 → misaligned.

Cheers, Lars

Click to expand...

Ghot said:

@LBN1405

I abuse my SSDs and HDDs regularly. The all divide by 4096 evenly.

Click to expand...

win11raider said:

I still use version 23H2 and follow the threads about its updates. After the preliminary update on October 28 (KB5067112), some users, but not all, reported decreased performance of their SSDs. I have forwarded your post to them to see if the problem they are experiencing is related to the misalignment you mention.

On the other hand, looking online at the reasons for misalignment, it is very rare for an update to cause it, unless third-party software is being used or Bitlocker is enabled. Of course, I'm no expert on this, but given the relevance of the issue, I'd like to know more about it.

By the way, how did you do the realignment?

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dgordon42 said:

I have a clean install of Windows 24H2, installed on a new NVMe M.2 PCIe SSD on a new computer. It updated to 25H2 via Windows Update last October.

It's first partition (EFI) is alinged, but the second (C:) and the third (Recovery) are not.

View attachment 155095

The disc runs at 50 C, and I have not noticed any performance problems.

Dave

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dgordon42 said:

— your C: drive is properly 4K aligned.
The partition starting offset: 122,683,392 bytes. When you divide that by 4096 (which is 4KB), you get a clean whole number:

No remainder means it's perfectly aligned.
Same goes for your Recovery partition — its offset is also divisible by 4096 without any remainder.
So your Windows install is correctly aligned on your NVMe SSD. You're good to go!

Click to expand...

LBN1405 said:

I have a EaseUS Partition Master usb live boot with 4K aligment. Be sure to make a backup first. And its very important to do the 4K alignment from a live boot usb and NOT with in Windows !!

Click to expand...

dgordon42 said:

I have a clean install of Windows 24H2, installed on a new NVMe M.2 PCIe SSD on a new computer. It updated to 25H2 via Windows Update last October.

It's first partition (EFI) is alinged, but the second (C:) and the third (Recovery) are not.

View attachment 155095

The disc runs at 50 C, and I have not noticed any performance problems.

Dave.

Click to expand...

dgordon42 said:

— your C: drive is properly 4K aligned.
The partition starting offset: 122,683,392 bytes. When you divide that by 4096 (which is 4KB), you get a clean whole number:

No remainder means it's perfectly aligned.
Same goes for your Recovery partition — its offset is also divisible by 4096 without any remainder.
So your Windows install is correctly aligned on your NVMe SSD. You're good to go!

Click to expand...