Windows 11 has a drive format built for source code, and it is faster
A ReFS volume with relaxed antivirus scanning. What it is for, what it costs, and whether it helps with space.
Dev Drive is a Windows 11 feature that creates a ReFS volume configured for development work. It is genuinely useful and it is worth understanding what it does and does not solve.
What it actually is
- A ReFS volume. A different file system from NTFS, with different characteristics for many small files.
- Performance mode antivirus. Defender scans asynchronously rather than blocking every file operation, which is where most of the speed comes from.
- Trusted by default. Marked as trusted so the relaxed scanning applies.
- Not bootable. It is for code, caches and build output, not for Windows.
Creating one
Settings, System, Storage, Advanced storage settings, Disks and volumes, Create Dev Drive. It can take unallocated space, shrink an existing volume, or use a VHD. The minimum is 50 GB.
What to put on it
| Good candidates | Why |
|---|---|
| Source repositories | Many small files, scanned constantly |
node_modules and package caches | The worst case for per file scanning |
| Build output | Written and deleted constantly |
| Container and image caches | Large and frequently rewritten |
# Point package managers at it
npm config set cache D:\dev\npm-cache
[Environment]::SetEnvironmentVariable('CARGO_HOME','D:\dev\cargo','User')
[Environment]::SetEnvironmentVariable('NUGET_PACKAGES','D:\dev\nuget','User')What it does not do
It does not save space. A file takes the same room on ReFS as on NTFS, and moving caches to it moves the problem rather than solving it. What it changes is speed, particularly for operations over thousands of small files, which is exactly what a build is.
The antivirus trade
Performance mode is a deliberate relaxation of real time scanning on that volume. On a development machine that is a reasonable trade and it is not free: code pulled from the internet lands there too. Knowing that is the point of it being a choice rather than a default.
The same reasoning applies to excluding source folders from Defender on an NTFS machine, which is the manual version and is covered in git on Windows.
Common questions
What is a Dev Drive on Windows 11?
A ReFS volume configured for development, with Defender running in performance mode so scanning does not block every file operation. It is meant for code, caches and build output.
Does a Dev Drive save disk space?
No. Files take the same space as on NTFS. It changes speed, particularly for operations across thousands of small files, which is what builds are.
How do I create a Dev Drive?
Settings, System, Storage, Advanced storage settings, Disks and volumes, Create Dev Drive. It needs at least 50 GB and can use unallocated space, a shrunk volume or a VHD.
Is a Dev Drive less secure?
Performance mode relaxes real time scanning on that volume, which is a deliberate trade. Code pulled from the internet lands there too, which is why it is a choice rather than a default.