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Provide a way to create clone/CoW copies #12902
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Likely needs libuv implementation. Related: libuv/libuv#925
Also see some of the attempts at using native copy calls in Yarn:
yarnpkg/yarn#3290 which uses https://github.com/sciolist/fcopy (Unix via a native module)
yarnpkg/yarn#2960 (Win32 via node-ffi)fs.copyFilewas added by #15034.FWIW, CoW is not supported yet. There is a PR to add it to libuv but I haven't landed it yet because I have yet to see it work on any of the CI machines.
Let's keep this open then.
Ponyfill fs-copy-file can be used for copying files. In
node.js<v8.5.0it copies files with help of streams and forv8.5.0and next versions it uses native implementation offs.copyFile.@coderaiser - That looks like a useful module. Although, technically that's not a ponyfill as ponyfills never use the native API (as per the document you linked to) 😃
Reacted by coderaiser
Currently, copying files is implemented by reading the data of the source file and writing it to the new file, see fs-extra's implementation of copy. The problem is that this approach doesn't allow the OS to optimize file copying (such as by using direct disk-to-disk copy if it's available), nor does it allow the (optional or by default) use of reflink/CoW.
I'm specifically interested in making CoW (which is already available on some *nix file systems, including btrfs and zfs) available to nodejs.
IMHO, nodejs should add an fs.copy function (just like what fs-extra already does) which is implemented using the OS native file copying syscall. It should have an optional
optionparameter that allows specifying the copy should use CoW (if available), just like howcp --reflink=autofrom coreutils works on Linux.Note that this would be particularly benefit for cases where files are copied often - particularly big files. I'm thinking that this improvement would substantially benefit package managers (npm, yarn, etc).