What Is Copy-on-Write (CoW)

Copy-on-write (CoW) is an optimization strategy used in memory managementfilesystems like Btrfs, when saving the current state of a virtual machine (VM), and in snapshot and backup operations.

When an entity or process intends to modify a shared resource, the system creates a distinct copy for that entity. The original resource remains intact and available to other entities. This approach conserves system resources by minimizing redundant data replication.

By delaying data duplication until the last possible moment, the CoW approach streamlines storage and memory usage and maintains data integrity.