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> If I snapshot the state of my cloud server, it creates a full copy of its disk in block storage somewhere, and takes several minutes to complete. Which cloud

> If I snapshot the state of my cloud server, it creates a full copy of its disk in block storage somewhere, and takes several minutes to complete. Which cloud provider are you using? Neither Amazon nor Google take snapshots this way. Amazon EBS and Google Persistent Disk both use copy-on-write semantics for snapshots. If you take a hundred snapshots of a 100 GB disk, your total usage is 100 GB plus metadata. When you run a VM instance from that disk, the storage usage will increase as blocks change, to a maximum of 200 GB total storage (for live disk + out of date snapshot). When I use QEMU or VirtualBox at home, I also get copy-on-write snapshots of disks, although it's certainly possible to get a full copy if you want. I think the feature is pretty standard.

crazygringo 6y ago
Digital Ocean. It absolutely takes snapshots by making a full copy: https://docs.digitalocean.com/products/images/snapshots/ https://docs.digitalocean.com/products/images/snapshots/ So this is a perfect example of what I mean by the word "snapshot" being used in two different ways by different people. Snapshot meaning "full copy" is one usage (Digital Ocean), snapshot meaning "diff checkpoint" is another usage (Google, AWS).
- klodolph 6y ago
  Those aren't different definitions of "snapshot", though.
  - crazygringo 6y ago
    Of course they're different. They have different meanings, so they're different definitions. It's not like it's the same concept with different hidden implementation details. On Digital Ocean, I can delete the server but I still have the snapshot. On the others, you can't. One copies, the other bookmarks. They're entirely different concepts, therefore different definitions.
    - klodolph 6y ago
      That’s an incorrect notion of “definition”. The concept of a snapshot is that you make a copy of something at a moment in time. That’s one concept, one definition, one meaning. You may fight over the details of the definition or the implications, but at most it means that you need to revise the definition a little bit, not that you need to add a new sense to the word.
      - crazygringo 6y ago
        > That’s an incorrect notion of “definition”. Nope, pretty sure different concepts means different definitions. Well -- or different "senses" if you want to be technical, but of course nearly everyone outside of dictionary editors uses "definition" to mean "sense". > The concept of a snapshot is that you make a copy of something at a moment in time. That’s one concept, one definition, one meaning. Except one of the two definitions isn't making a copy of anything. It's creating a new pointer to something that already exists, that's all. Zero copying. That's the entire point here. Which is why it's two concepts, two definitions, two meanings.

crazygringo 6y ago

Digital Ocean. It absolutely takes snapshots by making a full copy: https://docs.digitalocean.com/products/images/snapshots/ https://docs.digitalocean.com/products/images/snapshots/ So this is a perfect example of what I mean by the word "snapshot" being used in two different ways by different people. Snapshot meaning "full copy" is one usage (Digital Ocean), snapshot meaning "diff checkpoint" is another usage (Google, AWS).

klodolph 6y ago
Those aren't different definitions of "snapshot", though.
- crazygringo 6y ago
  Of course they're different. They have different meanings, so they're different definitions. It's not like it's the same concept with different hidden implementation details. On Digital Ocean, I can delete the server but I still have the snapshot. On the others, you can't. One copies, the other bookmarks. They're entirely different concepts, therefore different definitions.
  - klodolph 6y ago
    That’s an incorrect notion of “definition”. The concept of a snapshot is that you make a copy of something at a moment in time. That’s one concept, one definition, one meaning. You may fight over the details of the definition or the implications, but at most it means that you need to revise the definition a little bit, not that you need to add a new sense to the word.
    - crazygringo 6y ago
      > That’s an incorrect notion of “definition”. Nope, pretty sure different concepts means different definitions. Well -- or different "senses" if you want to be technical, but of course nearly everyone outside of dictionary editors uses "definition" to mean "sense". > The concept of a snapshot is that you make a copy of something at a moment in time. That’s one concept, one definition, one meaning. Except one of the two definitions isn't making a copy of anything. It's creating a new pointer to something that already exists, that's all. Zero copying. That's the entire point here. Which is why it's two concepts, two definitions, two meanings.