Can you explain the Copy-on-Write principle and how it works in data storage systems?

Copy-on-Write (COW) is a memory or data management strategy where copying of an object occurs only at the moment of its modification, not at the time of creating a copy.

In storage systems, it works as follows:

• Multiple processes or objects initially share the same memory area or data.
• As long as the data is not modified, everyone uses the shared copy.
• When an attempt is made to modify the data, an actual copy is made (a separate copy is created), and the changes are applied to it.

This approach helps save resources by reducing unnecessary copying.

Example: In file systems with snapshot support (e.g., ZFS), when a snapshot is created, data is not copied immediately but only when it is modified, which speeds up operations and saves space.