This Linux Storage Feature Feels Like Cheating Once You Understand It
How-To Geek, Sunday, June 28th, 2026
Copy-on-write filesystems enable efficient snapshots and clones by writing changes to new blocks.
Copy-on-write (CoW) represents a fundamental shift in how Linux filesystems manage data storage. Rather than immediately overwriting old data blocks, CoW filesystems write changed information to new locations and update pointers accordingly.
This enables powerful capabilities including snapshots, cheap clones using reflinks, and efficient rollbacks without full data duplication.
Btrfs is the most accessible Linux implementation, offering subvolumes, checksums, and send/receive functionality integrated into the kernel, while OpenZFS provides more mature storage-server features. The practical advantage becomes clear when creating virtual machine copies or taking system snapshots before risky operations, as unchanged data stays shared across file versions.