System snapshot is a crucial tool for data protection and system recovery. Today, I will start with COW file system, introduce four key features of Btrfs, and explain how to use Btrfs to take snapshots of your system. Copy-On-Write Copy-On-Write (COW) is an efficient storage management technique that ensures data integrity and optimizes storage utilization. When two processes simultaneously read the same data block in a COW file system, the system ensures that both processes access the same data block.