b00tkitism

Based on my research, Unraid's storage-related functionalities are largely open-source, but the way Unraid interfaces with its storage system is proprietary.
What’s Open Source?
The Unraid kernel module (md/unraid) registers two proc entries under /proc: mdcmd – Handles array creation, parity control, and other storage operations. mdstats – Provides status information about the array. The modified md driver (which implements Unraid’s parity-based storage) is released under GPLv2, meaning all storage-related operations at the kernel level are open-source. What’s Closed Source? The user-space communication with mdcmd is not open-source. Multiple components interact with mdcmd, including: The WebUI The emhttpd daemon (Unraid's proprietary management service) Mover Unraid Wake On Lan Daemon shfs (?) It does the same thing that MergerFS does. cgroup2-unraid (?) Other system scripts and services This means that while the storage driver itself is open, the logic that controls how Unraid manages and interacts with storage devices is proprietary.
Final Answer:
All core storage-related operations (parity handling, array management, etc.) are open-source. The closed-source part of Unraid is how it orchestrates storage devices and communicates with the kernel driver via mdcmd. Would love to hear thoughts from others—did I miss anything?