excitingburp, 1 year ago

Btw COW isn’t necessarily (and isn’t at least for ZFS) a performance trade-off. Data isn’t really copied, new data is simply written elsewhere on the disk (and the old data is not marked as free space).

Ultimately it actually means “the data behaves as though it was copied,” which can be achieved in many ways. There are many ways to do that without actually copying.