Windows 10 reserved storage explained

Martin Brinkmann
Jan 8, 2019
Updated • Jan 8, 2019
Windows, Windows 10

Microsoft revealed today that it plans to integrate a feature called reserved storage in Windows 10 version 1903, the next feature update of the operating system.

Windows 10 will set aside some available storage automatically so that it is  used exclusively by the operating system.

Through reserved storage, some disk space will be set aside to be used by updates, apps, temporary files, and system caches.

Microsoft wants to improve the reliability of "critical OS functions" that rely on disk space, e.g. updating or caching, by reserving disk space.

Existing devices won't have the reserved storage functionality enabled by default; new Windows 10 version 1903 installations and systems that come pre-installed with that particular version of Windows 10 -- and future versions -- will make use of reserved storage automatically.

windows 10 reserved storage

Microsoft notes that reserved storage will set aside about 7 Gigabytes of space; not a lot if Windows is installed on a device with lots of free storage but quite a lot if it is on a device with 16 or 32 Gigabytes of storage space.

The 7 Gigabytes that Windows 10 will reserve initially may change over time, and Windows 10 may use other space if the reserved storage is out of space.

The size depends on two major factors -- optional features and installed languages -- which are used to determine the reserved space.

Windows 10 users can check the size of reserved storage by going to Settings > System > Storage > Show more categories > System & Reserved. There you find listed the reserved storage that Windows 10 has set aside.

Administrators may reduce the size of reserved storage by removing optional features or languages, if installed. Reserved Storage may increase if additional features or languages are installed on a device.

It is not possible, however,  to remove reserved storage from the operating system. It is unclear if that means that reserved storage cannot be disabled anymore once activated, or if that just means that data that is stored in the reserved storage area cannot be removed by users.

Windows 10 will delete files in reserved storage regularly when they are not needed anymore

Microsoft published the following instructions to enable Reserved Storage on Windows 10 Insider Builds:

  1. Right-click the Windows icon on the taskbar, search for Registry Editor, and Open it.
  2. If prompted, select Yes to allow the app to make changes to your device.
  3. Select HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\ReserveManager.
  4. Right click ShippedWithReserves to modify and update the value to “1.”
  5. After you upgrade the device to the next available build, you will be using reserved storage!

A value of 1 means that Reserved Storage space is enabled, a value of 0 that it is not enabled.

It remains to be seen if it is possible to set the value to 0 on devices that come with Reserved Storage enabled to disable the feature and free up space.

How does it work?

Microsoft's explanation on Technet falls a bit short as it is not clear just from reading the article how Windows 10 reserves the storage space. Craig Barkhouse explains in a comment that Microsoft created a solution that adds "new support" for that to the NTFS file system.

The idea is NTFS provides a mechanism for the servicing stack to specify how much space it needs reserved, say 7GB. Then NTFS reserves that 7GB for servicing usage only.

Barkhouse notes that the main drive will report the available space and that the reserved storage is subtracted automatically from that.

Closing Words

The use of reserved storage should improve the reliability and stability of certain processes, e.g. updating; that is a good thing but the whole feature may make low storage devices running Windows 10 even less appealing than they are already.

Now You: What is your take on Reserved Storage?

Windows 10 reserved storage explained
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Windows 10 reserved storage explained
Microsoft revealed today that it plans to integrate a feature called reserved storage in Windows 10 version 1903, the next feature update of the operating system.
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  1. Nargiza Radjabova said on March 18, 2019 at 1:12 pm

    @exampler n.1

  2. John IL said on January 11, 2019 at 4:17 pm

    Um this seems counter productive on a cheap notebook with 32Gb of RAM. These were the devices already having problems upgrading because of the lack of storage. But now your adding a 7Gb reserve which may solve the upgrade issues, but creates yet another problem with personal file storage being much less. Not smart Microsoft to solve one issue and create yet another one. Honestly, nobody should buy a PC with Windows with any less then 128Gb of storage. Not these days, and Microsoft obsession with Chromebooks created these cheap and poorly thought out Chromebook killers with limited storage. Yeah 32Gb fine for a Chromebook, not fine for Windows PC.

  3. John C. said on January 11, 2019 at 11:19 am

    Yet ANOTHER reason why I wouldn’t touch Windows 10 with a barge pole. Microsoft is a monopoly gone wild, needs to be broken up.

  4. Clipper87 said on January 10, 2019 at 4:15 am

    Apart from pre-allocating 7 GB what would be the difference with the current C:\Windows\SoftwareDistribution folder ?

  5. Uncensored said on January 9, 2019 at 12:55 pm

    Bloatware install storage.

  6. John C. said on January 9, 2019 at 11:27 am

    I’ve long thought that Microsoft might be stealing processing cycles from computers, using them to create a kind of collective supercomputer. It would be doing this by using hardened IP addresses and rootkit technology. Thus the push for multiple processor CPUs and now, reserved hard drive space. I’m not saying that this is happening for sure, just that it’s a possibility.

    1. John Fenderson said on January 9, 2019 at 8:27 pm

      @John C: Honestly, given the economics involved, I think it would be cheaper and easier for them to just set up their own massively parallel system rather than siphon off cycles from users.

  7. Anonymous said on January 9, 2019 at 11:07 am

    Absolute cancer. W10 already takes up too much space for an OS.

  8. No Updates No Problems said on January 9, 2019 at 5:54 am

    Looks like another update to skip. And I was hoping maybe this would be one worth updating to. Guess my prediction that nothing good will happen to Win 10 at least until 2020 is coming true. It’s still basically a beta, an unfinished product. Look at what they’re doing, they are still tweaking key features like Update. They shipped Win 10 without fully testing something as critical as the servicing stack which is the key to the whole Windows “service”. On top of that the Store and the UWP format is also still screwed up in many ways. Two of their key features are not ready three years later. All this time Microsoft used the public as beta testers, not caring how many systems their experiments trash, how much time and work people and businesses lose.

  9. John G. said on January 9, 2019 at 4:31 am

    Another nail in the coffin of the W10 user’s confidence. Too bad, imho, for the little notebooks (my sister has one with 64Gb of disk space). My grandfather often said “if you have two broken legs, your headache is not your big problem, my little boy”. He was always a very clever man.

  10. Cinikal said on January 9, 2019 at 3:22 am

    CompactOS always, 16mb min 1gb max pagefile, all but store app removed will get me 8.5 gb at boot, and this is 32bit. Will be leaving the tablets on 1809.

  11. Yuliya said on January 8, 2019 at 10:33 pm

    Bad. Why do you need ro “reserve” 7 GiB of space for Windows Updates? It’s not like this is all I do with my PC. Let other programs use that space for their own temporary files. Programs which the OS might not even be fully aware of, such as portable ones.

  12. ilev said on January 8, 2019 at 6:46 pm

    So, after grabbing 10sGB with winsxs, sleep, hibernation..Microsoft wants another pound of storage flesh.
    Will wait for a hack to block it.

  13. chesscanoe said on January 8, 2019 at 5:53 pm

    It is amazing, if not surprising Microsoft neglected to implement this design until 2019. No wonder lower severity bugs still are not fixed – even big potential problems seem to be ignored as long as possible.

  14. crambie said on January 8, 2019 at 5:47 pm

    That’s more than 4 times the hard drive requirements for XP about half of Windows 7. Many people won’t care but these 64GB tablets etc will.

  15. LTL said on January 8, 2019 at 5:38 pm

    Typo, Martin: “Windows 10 will set aside some available storage automatically so that it IS CAN BE used exclusively by the operating system.”

  16. John Fenderson said on January 8, 2019 at 5:30 pm

    The concept of reserved storage is fine, and it’s hugely good that this won’t be forced on existing installs.

    The lack of flexibility seems to be a bit of an issue, though. I wonder how this is implemented? If they’re just going to make a separate partition for it, then it might be possible to resize that partition to reduce (or expand, if disk space isn’t an issue) the amount of space lost to this.

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