I've been running into Windows 11 update failures lately, particularly with versions 23H2, 24H2, and 25H2. The errors point to system space issues, but my C: drive has plenty of free storage. After digging deeper, I found that the root cause is my System Reserved Partition (SRP) or EFI partition being only 100MB, which seems inadequate for the newer Windows updates. Many machines affected were built from older deployment images. It's frustrating because Windows tries to write additional boot and recovery data, leading to silent failures when it runs out of space.
So far, my temporary fix involved mounting the EFI partition and deleting some non-critical font files to free up space—this worked, but I want to ensure it's not just a short-term band-aid. I'm curious about long-term solutions:
- Is anyone rebuilding images with a larger SRP (like 300-500MB)?
- Have you safely scripted SRP resizing at scale?
- Are others just accepting this as a recurring maintenance task?
I'm hesitant to resize EFI partitions on live machines without proper tools. I'd appreciate any best practices, experiences, or warnings to avoid.
4 Answers
When you do a clean installation of Windows 11, it typically creates a 100MB EFI partition which should be sufficient. However, hardware manufacturers like HP and Lenovo often clutter it with BIOS updates, which can fill it up and block further updates. You can mount the EFI using a command like `mountvol s: /s`, delete unnecessary directories, then remount to allow updates. Resizing the EFI partition usually requires deleting the recovery partition at the end of the disk and creating a new one, which involves copying content or using `bcdboot`.
We've noticed this issue too, but only on a few machines. We concluded that it stems from Microsoft overlooking the need for larger partitions as updates roll out. For those devices, a fresh reinstall of the latest Windows 11 image worked best since they were end-user machines. Sometimes starting fresh is just more efficient in such cases.
While it may seem scary, I’ve found that shrinking the C: volume, creating a new FAT32 EFI partition from the freed-up space, and using the `bcdboot` command is a viable approach. However, in practice, it's usually safer to tackle this situation upon acquiring or redeploying machines. It’s often easier just to redeploy if you’re trying to fix this quickly!
Resizing is straightforward if you have enough free space on your C: drive and allow it to shrink properly. Just make sure to move the C: partition to create space for at least a 260MB EFI partition (300MB if you're using native 4K drives). And don't forget about the Microsoft Reserved (MSR) partition that needs to be accounted for too. Scripting this process is totally feasible, and I suggest using WinPE for the task.
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