Windows Dev Drive

A Dev Drive is a ReFS volume with developer-specific file system optimisations, a trusted flag, and control over which minifilters attach. On a trusted Dev Drive, Microsoft Defender runs in performance mode — scans are deferred until after the file open completes (async) instead of blocking it (sync). Microsoft measures large wins on clone, restore and build; the biggest single factor is that build output and package caches stop being scanned synchronously.

Start with the audit. Most machines already have a Dev Drive that is mis-tuned rather than missing.

powershell -ExecutionPolicy Bypass -File scripts/Test-DevDrive.ps1

Read-only. Reports prerequisites, machine policy, per-volume trust and attached filters, Defender performance mode, Defender exclusions that overlap the drive, and which package caches still live on C:. Ends with a numbered list of fixes.