Copy on Write

When I first encountered ZFS it felt like black magic with its instant snapshots AND self healing checksums. I was told it’s all thanks to Copy-on-Write (CoW). Years later, I’m writing this post to explain this strategy, as it’s one of my favorite optimisation techniques. By the end, you’ll see how CoW is more than just a trick; it’s the fundamental design choice that solves some of the trickiest problems in performance, concurrency, memory usage, and data integrity, all while keeping things blazing fast.