throw0824a
It does make sense: one is writable and the other is not. When someone is talking about (e.g.) mitigation mechanisms against ransomware, saying you have "snapshots" is meaningless if they're R/W as the ransowmare can go in an overwrite files. But if you use the term "snapshot" correctly--meaning R/O--everyone involved knows you have mitigated the risk since the data is safe from being altered and reverting is possible.
It's not the "same thing" if there is a difference between the two--which there is, the R/O flag setting. If two thing are different then they are not the "same": this may seem tautological but it's not. Call different things differently.
The btrfs CLI is really retarded in this regard where using "snapshot" is not R/O by default, as it violates decades of expectations and POLA:
* https://en.wikipedia.org/wiki/Principle_of_least_astonishmen...
Yup, this is my point: words have meaning.
Semi-recent XKCD on "Communicating":
You can do this with ZFS as well.
First, there is no such thing as a "rewritable snapshot"; the term is an oxymoron. Please do not use it and please do not promulgate it. The term "snapshot" should be reserved for read-only states of a (file) system at a particular point of time:
* https://en.wikipedia.org/wiki/Snapshot_(computer_storage)
Second, ZFS does have this feature: its called cloning. You create a (read-only) snapshot, and then run the "clone" command to make it read-write:
* https://www.freebsd.org/doc/handbook/zfs-zfs.html#zfs-zfs-cl... * http://docs.oracle.com/cd/E19253-01/819-5461/gbcxz/index.htm...
As long as the clone exists though, the snapshot cannot be deleted. However you can "promote" the clone, after which the snapshot can be removed. This feature has been around since at least 2010:
* https://www.freebsddiary.org/zfs-promote.php
Please use the word "clone" for a read-write copy of an original data set, as it is already fairly accepted nomenclature:
* https://en.wikipedia.org/wiki/Disk_cloning * https://en.wikipedia.org/wiki/Cloning_(programming)