My C: Drive Hit 70 MB Free. Here's What I Did About It.
Here’s the deal - my C: drive hit 70 MB free. 475 GB drive. Not great.
I’d been ignoring this for months. My source code was on D:, so I kept thinking “how is my C: drive full?” Turns out my package caches - npm, NuGet, Go, pip, pnpm - were still on C:. Years of cached packages, all on my system drive. Builds started failing because there wasn’t enough temp space.
I’d heard about Windows Dev Drive but never set it up. One of those “eventually” things. Eventually came when I couldn’t build anymore.
What’s a Dev Drive?
Dev Drive is a ReFS volume with a special Defender “Performance Mode” that scans files asynchronously instead of blocking every read/write. If you’ve ever watched node_modules install and wondered why it’s so slow, a huge chunk of that is your antivirus scanning thousands of tiny files one by one. Dev Drive fixes that.
ReFS is optimized for the kind of workloads developers throw at it - tons of small file I/O, constant reads and writes, deep directory structures. Combine that with Defender scanning in the background instead of blocking, and things get noticeably faster.
Setting It Up with Copilot CLI
I pointed Copilot CLI at the Dev Drive documentation and said “set this up for me.”
Here’s what it did:
- Created a 250 GB VHDX - a virtual hard disk that lives as a file on my D: drive
- Formatted it as ReFS - the file system optimized for dev workloads
- Set up auto-mount on boot - so the drive is always available after a restart
- Moved my source code over - from D: to the new Dev Drive
Then I had it move all my package caches to the new drive and configure the environment variables so everything pointed at the right location:
- Go modules (
GOPATH,GOMODCACHE) - Go build cache (
GOCACHE) - NuGet (
NUGET_PACKAGES) - pip (
PIP_CACHE_DIR) - npm (
npm_config_cache) - pnpm store (
PNPM_HOME, pnpm store path)
Two minutes. That’s how long the conversation took. I should’ve done this months ago.
The Results
Builds are noticeably faster. npm install, go build, dotnet build - all faster. Git operations are snappier too. Microsoft says about 25% improvement for dev workloads. That tracks with what I’m seeing.
Package caches rebuild automatically if anything goes wrong. Delete your npm cache and it re-downloads next time you install. Same with Go modules, NuGet, pip. Zero risk in moving them.
And my C: drive? Plenty of room again.
Try It
If you’re on Windows 11 - open Copilot CLI, paste the Dev Drive docs link, and tell it to set up the drive. Then tell it to move your package caches. That’s it. Faster builds, faster installs, faster git.
I should’ve done this a year ago.