New installs of Windows 10 1903 will take 7GB of reserved space or more if required.

6pack

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Source: The Register UK

Microsoft has announced that it is formalising the arrangement whereby Windows 10 inexplicably swipes a chunk of disk space for its own purposes in the form of Reserved Storage.

The theory goes like this – temporary files get generated all the time in Windows, either by the OS or apps running on the thing. As a user's disk fills up, things start getting sticky as space for this flighty data becomes short and reliability suffers.

Microsoft has tried a few ways over the years to help users manage disk space – Windows will start to whinge as disks reach capacity and built-in tools exist to clear unwanted files. The latest, Storage Sense, will quietly "dehydrate" OneDrive files to free up space.

It appears that such tools aren't enough.

In 2019, Microsoft is throwing in the towel. New installs of Windows 10 1903 (currently with Windows Insiders in the form of 19H1 and expected in the hands of users sometime in April) will feature "Reserved Storage".

Reserved Storage effectively blocks out a chunk of disk for temporary files generated by the likes of apps or OS updates. The gang at Redmond reckons that 7GB of sacrificial space will be a good starting point, but the total might vary over time. You can also shrink the reservation, but never remove it from the OS entirely.

Users can then cheerfully use their PCs without worrying about their free space suddenly disappearing as a colossal Windows update gets silently downloaded in the background. That space has been pre-nabbed ready for all those temporary(ish) files.

Unless, of course, the Reserved Storage fills up. In which case it will be business as normal as Windows temporarily consumes space outside the reservation, thus somewhat defeating the point of the thing.

Slightly ominously, Microsoft also said: "We may adjust the size of reserved storage in the future based on diagnostic data or feedback."
 

kuduku

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Wow!! In past 2yrs my 120gb C partition is already 84gb used (user data just 12-15gb) and now this.
Cant afford to loose precious space for windows operations.

A registry tweak will very well take care of this.
I dont know about your setup but my complete C drive is only 26GB on SSD excluding user data. Cleanup is required seems
 

6pack

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A registry tweak will very well take care of this.
I don't think any registry tweak will work. That reserved space is like a new hidden partition before the Windows C drive. So in new hardware, during installation of Windows 10, 100-500MB will be EFI partition, ~7GB of space will be a hidden partition or volume and the rest will be C drive.

For existing installations, I think it may not be made or Windows might very well do it without notice if there is enough space on C Drive when installing some huge update.
 

vishalrao

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If reserved space is a partition then this can cause dismay among linux dual booters. Already I see 3 partitions created by windows, 1.recovery, 2.efi and 3. C drive.

4th remaining partition i use to create an extended partition which can hold multiple logical partitions for multiple linux installs. if 4th partition is also gone now then no more space to create for linux!

this limitation of 4 primary partitions is for old MBR partitioning scheme though, i think GPT does not have this restriction.
 

6pack

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Windows 10 does GPT volumes only I think. In my old drive which I deleted to make way for linux, in a new install there was 350MB reserved space for Windows as a hidden partition after the EFI partition. This is what I remember. I think they are expanding this 350MB partition to 7GB or more on new installs and devices like laptops etc.
 

Marcus Fenix

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Wow!! In past 2yrs my 120gb C partition is already 84gb used (user data just 12-15gb) and now this.
Cant afford to loose precious space for windows operations.

A registry tweak will very well take care of this.
Go to Settings>System>Storage>Free Up Space Now.
In my experience installed Windows Update leftover files,old Windows versions and Delivery Optimization files take up a lot of space and I clean it regularly so that my C Drive has 25.7 GB free out of 50 GB on my headless file server. Please note that this cleanup takes quite a bit of time but I am running a quad core 1.5 GHz Atom so that might be the culprit.Don't remember the timings on my Ryzen 1700 rig to compare though.

P.S. I always move the personal folders(Documents Downloads etc.) to other drives to ensure my weekly scheduled Windows image backups contain program installations only and are smaller in size.It also lets me restore Windows installation image in case of problems without worrying about any personal files as they are in different partitions,