W11 Partitions mystery

W11 Partitions mystery

I clean installed W11pro on a Dell 7010 using Rufus to avoid TPM, SecureBoot, Bitlocker, MS Acct. I wanted GPT/UEFI but forgot to
select this and ended up with a legacy MBR install of W11. After booting W11 I used the mbr2gpt utility, switched to UEFI in BIOS,
and after reboot I checked with msinfo32 to make sure it was now UEFI. There are a few confusing things about what Disk Manager
shows:

The partitions are in a different order than shown in the "Default UEFI/GPT Hard Drive Partition Layout" post on this site.
Instead of EFISystem,MSR,Windows,Recovery I seem to have MSR,Windows,Recovery,EFISystem. This was probably caused by the steps
I used. I can go back and recreate the install media as GPT/UEFI to get the preferred order, or maybe there is a way to force
it even with MBR target install media?

Another issue is it seems the MSR? partition was assigned drive letter D. My understanding is the MSR and EFISystem partitions are
not meant to be user accessible so why give them drive letters? Further confusion is if I look at the Storage use for D: it holds
System & Reserved stuff as expected but also some document(s) as if it really were a general use partition. Any insights?

By examining partition IDs and flags, Disk Manager is able to provide some useful info to identify what each partition is about,
such as "Boot","Recovery","EFI System", but the only thing it offers up for this "D:" partition is "Basic Data", when it should
probably be saying MSR or System. Good luck using disk utilities without useful partition identifiers.

Mine shows like the above the last partition in From Dell , if I wanted to restore it to how it was on install. I would have to say that yours is OK you can remove the letter D from it. My partitions are larger due to have a 2TB drive.

After a clean install on an unallocated drive, with all other drives unhooked... this is the default Win 11 UEFI install...





And... here's ten points just for filling out your computer specs.

The first partition was originally the System partition on an MBR disk. In Windows 10 22H2 Setup, a 50 MB System Reserved partition is created on MBR disks, whereas Windows 11 24H2/25H2 Setup creates a 100 MB System partition on MBR disks (the label is no longer “System Reserved”).

If the existing MBR system partition isn't reused for the EFI system partition, it's no longer used by the boot process after the conversion.

If the existing MBR system partition isn't reused for the EFI system partition, it might be assigned a drive letter. If this small partition isn't going to be used, its drive letter must be manually hidden.

Click to expand...

This last post convinces me that my partition disorder is a result of starting with a legacy format and then using the mbr2gpt tool. It would probably continue to work fine, but I would rather the windows and recovery partitions be last in line. I will reinstall W11 from a GPT/UEFI media and report back.

When performing MBR2GPT the command results in a conversion but the partition order may have different results.

This happens when the MBR2GPT is performed while not in Windows RE.

To get the desired normal partition order > create a Macrium backup image > clean install Windows 11 > restore only the C: partition

Macrium Software | Your Image is Everything


Backup and Restore with Macrium Reflect

tns1 said:

This last post convinces me that my partition disorder is a result of starting with a legacy format and then using the mbr2gpt tool. It would probably continue to work fine, but I would rather the windows and recovery partitions be last in line. I will reinstall W11 from a GPT/UEFI media and report back.

Click to expand...

Clean installed W11p again from Rufus but this time for a GPT/UEFI target and it produced the proper partition order without the odd extra 'basic data' partition, so no extra drive letter being assigned. The MSR partition is not visible here but it is present as partition 2, and visible in tools like Macrium, Gparted, Diskpart.

Looks normal.

The Recovery partition should be at least 750M.

It looks better now.

Windows would have worked fine before as well, since the EFI system partition does not need to be the first partition on the disk.

In addition, the absence of a 16 MB Microsoft reserved partition (MSR) would not have affected functionality, because Windows does not use that partition for anything.

^ Windows uses the MSR for:

• compatibility: It acts as a placeholder for features that used to rely on hidden sectors on older MBR disks. Microsoft can later shrink the MSR to create new partitions for these components.
• basic partition management: It is used to remap damaged sectors on the drive.
• advanced features: When a basic disk is converted to a dynamic disk, Windows shrinks the MSR and uses the freed space to create a partition to hold the dynamic disk database.
• system support: It provides a dedicated space for system software that might need to create new partitions for its own use, such as boot and recovery processes.

If the MSR partition is absolutely necessary, why doesn't the MBR2GPT command create an MSR partition?

ChatGPT:

Why doesn’t MBR2GPT create an MSR partition, if the MSR is supposed to exist on GPT disks?​

Because the MSR is not required for booting Windows, and MBR2GPT’s purpose is limited:
convert the disk layout
make Windows boot in UEFI mode
not reorganize the disk to match the exact clean-install partition layout

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Details​

The Microsoft Reserved Partition (MSR) exists only on GPT disks used by Windows.
Its purpose is not to store files. Instead, it functions as internal workspace for the partitioning system — for example, to allow creating new partitions without needing to move metadata.

• Windows Setup adds an MSR only during a clean install.
• Windows never boots from the MSR, and Windows does not read/write user data there.

From Microsoft’s documentation:

The MSR is required for “proper partition management”, not for booting.

Click to expand...

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MBR2GPT.exe specifically​

MBR2GPT’s job is narrow:

Convert the existing MBR partitions to GPT and add an EFI System Partition so the system can boot using UEFI.

Click to expand...

It does not attempt to change your existing partition layout beyond what is absolutely required to boot.
Because Windows doesn’t need the MSR to boot, MBR2GPT skips creating it.
Or in simpler terms:

MSR is useful, but not required for Windows to function — therefore MBR2GPT doesn’t bother creating it.

Click to expand...

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So who is right — the “necessary” or the “not needed” people?​

Both, depending on context:

Context	Is MSR required?
Clean install of Windows	Created automatically (recommended)
Booting and running Windows	Not required
Conversion using MBR2GPT	Not created, not needed

Click to expand...

I have to agree with hdmi and aubergine
I always create the MSR partition. Is so small and MS says it's necessary, so why not?
A MS toll like mbr2gpt doesn't create the MSR partition so it suggest it is not necessary.
Anyway, when I use the mbr2gpt tool offline it is normally to convert Win 7 or Win 10 from MBR to GPT and It use a big System partition to create the EFI partition and I manually create on the remain unallocated space the MSR partition