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August 14, 2020

Thank you, Microsoft – An Important Change in Windows Setup

Needing screenshots of Windows Setup for a new tutorial, I accidentally noticed today that Microsoft has finally changed its default partitioning of the system disk to comply with their own partitioning guidelines. The title image above shows how Microsoft recommends a GPT disk be partitioned.

Until recently, and still in Windows 10 versions 19H1 / 1903 and 19H2 / 1909, Windows Setup created the WinRE (Recovery, today by default OEM) partition on GPT partitioned disk at the beginning of the disk, followed by the EFI and MSR partitions, and putting Windows partition last as partition 4. This automatically causes additional WinRE partitions to be created, whenever a future feature upgrade needs to increase the size of the WinRE partition. If it’s the first partition on a disk, directly followed by EFI partition, there’s no space for it to expand. In the screenshot, the original WinRE partition (yellow highlight) could not expand when a feature upgrade required more space, so a new one was created following the Windows partition (blue highlight):

This screenshot comes from a story about this anomalous behaviour in Windows Setup that I wrote in April 2019: Why do I have multiple Recovery Partitions? – The Explanation

Here’s a quote from that story:

There’s a fundamental flaw in Windows 10 Setup when performing a clean install on a new empty hard disk or SSD. The same is true when wiping the disk empty on a device containing a previous Windows 10 installation and deleting all partitions and performing a clean install. The flaw is, Windows Setup positions the small but important 500 MB recovery partition first on the system disk. If and when future feature upgrades need more space to store the recovery environment, the recovery partition cannot expand, and a new recovery partition is created.

But, today when letting Windows Setup partition the system disk while installing latest Fast Ring Insider build 19023, I noticed a minor change with some major impact. Here is Windows Setup before the change, after letting Setup partition the GPT system disk:

Notice the WinRE partition in first place in that disk layout. By contrast, here’s how it looks now in recent Fast Ring builds:

The biggest change is that the WinRE partition is not created at this stage. Windows Setup creates only EFI, MSR and Windows partitions at first, installs Windows, and only then creates the WinRE partition following the Windows partition. It marks the end of users questions about multiple WinRE partitions. When placed immediately after the Windows partition, the WinRE partition can something no other partition can. It can expand backwards “stealing” the extra space it needs from the C: partition. The next screenshot shows how it expands (green highlight) when extra space is required in some future feature upgrade:

Unfortunately, normal Windows 10 users must wait for this change until version 20H1 is released.

I was interested to figure out when this change was made. I normally deploy instead of clean install, answer files taking care of everything including partitioning. I can’t even remember when I last performed a traditional clean install before today. My Insider ISO storage is missing some older ISO images, but I found out that Build 18875, released the same day (April 10, 2019) I published my story about this anomaly, still creates the WinRE partition in the wrong place, up first on disk. In Build 18898, released on May 15, 2019, the change is present and the WinRE partition follows the Windows partition. In between those two builds, three other Fast Ring builds were released: 18890, 18894 and 18895. The change, as far as I can tell, must have been made in one of those three builds, or perhaps in build 18898 itself.

Whatever it was that made Microsoft change its Windows Setup default partitioning, I don’t care. The main thing is, partitioning now follows Microsoft’s own GPT partitioning guidelines. This is an emphatically positive change: thank you Microsoft!



Author: Kari Finn

A former Windows Insider MVP, Kari started in computing in the mid 80’s writing code for VAX / VMS systems. Since then, he’s worked in a variety of IT positions. He specializes in Windows image capture, customization, repair and deployment as well as Hyper-V virtualization. Kari is a proud Team Member at number #1 Windows site TenForums.com.

10 Responses “Thank you, Microsoft – An Important Change in Windows Setup”

  1. Toni Fasth
    November 18, 2019 at 19:03

    This is awesome news. I was wondering how long it will take for them to update the installer so it follows MS own recommendations.

    • November 19, 2019 at 16:51

      Yes, it really is good news!

  2. Nathanaël Lacourly
    February 12, 2020 at 15:02

    next step would be, how to do it with wsim autounattend.xml ? which is currently impossible, right ?

  3. Nathanaël Lacourly
    February 16, 2020 at 20:17

    Thanks Kari, i already read it. But for me it is not applicable because it would need to create an autounattend.xml per device with same size of disk. But thank you for the answer !

    • February 16, 2020 at 20:53

      You could try MDT (Microsoft Deployment Toolkit), that’s what I use. I wholeheartedly recommended it, not only for IT admins but also for private users. It partitions the disk correctly, and makes deployment easy. See this: Windows Deployment with MDT – Part 1: Setup

  4. Nathanaël Lacourly
    February 19, 2020 at 13:25

    thanks, i will take a look tonight. It seems to be the only last way 😉

  5. Nathanaël Lacourly
    February 19, 2020 at 13:31

    I couldn’t wait, I browsed the subject (link about MDT) and it seems much more affordable presented as well. As soon as I have a few hours free I set up my lab to try. Thanks again for your time for us.

    • February 21, 2020 at 02:58

      Let us know how your tests go!

  6. BrokenLawShaw
    July 11, 2020 at 13:15

    What about older systems with MBR partitions? Does it remains unchanged for them?

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