Feature #5778

Updated by Peter Amstutz over 4 years ago

Keep can perform efficient copy-on-write of files and directories, but standard POSIX semantics don't offer a way to specify COW (copy on write) link semantics. We've decided not to abuse standard hardlinks because we can't actually provide POSIX conforming behavior.

Establish a protocol to ask for COW copies from the FUSE driver. This could be one of:

* Use BTRFS clone ioctl() (requires support for handling ioctl() in llfuse). User can use @cp --reflink@
* Use s3fs approach of writing a special xattr() to a special place to request a COW link. User uses a custom command to communicate with the file system.
* Determine source and target collections, perform the operation using Arvados SDK. Also requires a custom command. Results show up in target directory on refresh.