System reserved partition

[Octopuss]

It wasn't until yesterday that I realized the cumulative updates keep failing to install because - judging by some random google results when I googled the 0x800F0922 or 0xc1900104 error - there's no reserved partition, you know, that 500MB thing, on my system. I have my unattended installation that I've been using since Windows 7 and it always worked just fine. I started seeing CUs fail to update some time during last year and always thought it was because my system got somehow was broken after over two years of torturing it.

Does anyone know when has that partition became a requirement? I don't understand it anyway, what does the partition do for the updates? Interestingly, manually installing the CUs work fine,.

Edited March 13, 2021 by Octopuss

[Tripredacus]

It hasn't been a real requirement from MS to use a System Partition, at least not to the end user. It has been in every instance of installation guidance since Vista for MBR and is a requirement for GPT disks. But note that while it is "System Reserved" on MBR, it may not be called that on GPT.

Are you using MBR with 1 partition?

Post a list of paritions on your disk, perhaps you do have one but is instead, full.

[UCyborg]

At least on MBR systems, if you have prepartitioned disk with a single boot partition, you can install the whole OS on it without any problem by selecting said partition in installation wizard, where everything is installed.

If you have unpartitioned disk and select unpartitioned space, it will create several partitions. The default layout was changed several times, it started with small "System Reserved" partition, then the size of it was increased as recovery image (WinRE) grew in size.

In latest iterations of the OS, the default layout includes 50 MB partition with boot files, 2nd partition accommodating operating system and the 500 MB (it's actually 498 MB in my test virtual machine) 3rd partition with WinRE.

It's odd that cumulative update would complain about the reserved partition, especially in a single boot partition scenario, but OS upgrades do pose at least one question from updating component POV in a scenario where such partition exists, eg.: "What do I do if I can't fit the new recovery image on the old "System Reserved" partition?".

Edited March 15, 2021 by UCyborg

[Octopuss]

I have just tried this in a VM and sure enough, once that partition existed, the CU installed just fine. If it's not present, it fails during reboot after seemingly successful installation.
This started some time a few months ago, basically in the 2nd half of last year I guess.

I have the usual GPT setup with 100MB EFI, 128MB MSR, and the actual Win partition. I have been doing this for years and it only started to give me problems with this thing.
Oh and btw, installing a CU manually works just fine even without the partition. That's kinda bizarre.

Something must have changed somewhere but... meh.

Edited March 21, 2021 by Octopuss

[Tripredacus]

19 hours ago, Octopuss said:

I have the usual GPT setup with 100MB EFI, 128MB MSR, and the actual Win partition

The EFI partition is the "system reserved" partition it is referring to.

[Octopuss]

It seems like it isn't.

https://docs.microsoft.com/en-us/windows-hardware/customize/desktop/unattend/microsoft-windows-setup-diskconfiguration-disk-createpartitions-createpartition-type and https://docs.microsoft.com/en-us/windows-hardware/customize/desktop/unattend/microsoft-windows-setup-diskconfiguration-disk-modifypartitions-modifypartition-typeid

[Octopuss]

Update:

The updates kept failing because I uninstalled (and blocked from reinstalling) Edge. Yes. What the F***!!! Microsoft will never change.