Reserved Storage sets aside 7 GB you are not allowed to use
Windows reserves space for updates and hands it back to nothing. What it costs, how to read it, and the one command that turns it off.
On a drive that is nearly full, several gigabytes are already promised to something you will never see in Explorer. Reserved Storage is a block of space Windows sets aside for updates, temporary files and system caches, so that an update cannot fail for lack of room.
It is a reasonable idea with an unreasonable footprint on a small drive. It starts around 7 GB and grows with the optional features and languages you have installed.
Reading what it is actually holding
DISM /Online /Get-ReservedStorageState
# What Windows thinks the whole picture is, including the reserve
Get-Volume -DriveLetter C | Format-ListSettings, System, Storage shows the same figure inside System and reserved, which is where most people first meet it and assume it is Windows itself. It is not: the operating system files are counted separately, and the reserve is the part that is empty by design.
What it changes when it is on
| With it on | With it off |
|---|---|
| Updates install into space already set aside | Updates use whatever is free at the time |
| The reserve shows as used, always | The space shows as free until something needs it |
| An update rarely fails for space | An update on a full drive can fail outright |
| Temporary files are absorbed by the reserve | Temporary files count against your free space |
Turning it off, and what you accept by doing it
# Elevated PowerShell. Refuses while an update is pending.
DISM /Online /Set-ReservedStorageState /State:disabled
# Back on again
DISM /Online /Set-ReservedStorageState /State:enabledThe command refuses if an update is part way through, which is deliberate and worth respecting rather than working around. Once disabled, the space returns to your free total at the next restart.
What you give up is the guarantee. On a machine that already struggles for room, turning off the reserve makes the free number look better and makes an update failing for space more likely, which is the exact problem the reserve exists to prevent.
When it is worth doing
- A 128 GB laptop or tablet, where 7 GB is five percent of the whole drive and every gigabyte is fought for.
- A machine with a second drive, where an update can be pointed at space elsewhere.
- Never on a drive with plenty free. You would be trading a real safety net for a number you were not short of.
If the drive is tight enough for this to be tempting, work through what is actually filling the C drive first. The reserve is a fixed 7 GB, and on most machines there is more than that sitting in caches nobody has looked at.
Common questions
What is Reserved Storage in Windows?
Space Windows sets aside so that updates, temporary files and system caches always have room. It starts around 7 GB and grows with installed optional features and languages. It shows as used even when nothing is in it.
Is it safe to disable Reserved Storage?
It is supported and reversible, using DISM /Online /Set-ReservedStorageState /State:disabled from an elevated prompt. What you lose is the guarantee that an update has room, so it is a reasonable trade on a very small drive and a poor one otherwise.
Why can I not disable Reserved Storage?
The command refuses while an update is pending. Finish or cancel the update, restart, and try again.
Does disabling Reserved Storage free space immediately?
Not until the machine restarts. Check the state with DISM /Online /Get-ReservedStorageState afterwards rather than trusting the free space figure straight away.