copy-on-write
nounUK /ˌkɒpi ɒn ˈraɪt/
US /ˌkɑːpi ɑːn ˈraɪt/
A way for computers to share the same data until someone needs to change it, and only then make a separate copy.
The file system uses copy-on-write so that snapshots take almost no extra space.
OTHER MEANINGS
2. A programming technique where a copied object shares data with the original until one of them is modified.
The string class implements copy-on-write to avoid unnecessary allocations.
3. A storage strategy in which blocks are duplicated only when they are about to be overwritten.
Copy-on-write lets the backup system store thousands of versions cheaply.
4. A process model where a forked child process shares the parent's memory pages until either writes to them.
Linux uses copy-on-write when a process calls fork().