reflink(3c) What is it? Why do I care? And how can I use it?

Oracle Solaris 11.4 Beta is now available. One of the most requested features may seem like a tiny thing, but could have a huge impact on your VM deployments, or if you happen to deal with very large files regularly (eg video files).

Copying files is usually a case of telling the file system to read the blocks from disk, then telling them to write those same blocks to a different bit of the disk. reflink(3) allows you to tell the file system to simply create a new mapping to those blocks from a file system object (ie a file). ZFS will then keep track of any changes you make to the new file and write a copy of the modified blocks as part of the new file only. This is essentially like ZFS file system snapshot and clone, but on a file level.