The benefit of using this procedure can be quite substantial when snapshot support is enabled on the destination volume. Consider two alternatives. Suppose you have a 40GB VM container file that changes every day, but only about 1GB of data within that file changes in any given day. If CCC were to recopy that whole file every time it changes, then every snapshot would uniquely reference at least 40GB of disk space. This will add up quickly, and will impose a lower practical limit on the number of snapshots that can be retained. When using the clonefile procedure, however, only the blocks that have been modified on the source will be modified on the destination, so the 1GB of daily changes to that VM container file will have a very low net impact on snapshot disk usage.

Sometimes it's handy to make a full, complete, exact copy of one of your Mac's drives - especially the Startup Disk. Due to the complexity of macOS's UNIX underpinnings and the huge number of files installed with macOS, making a disk clone can be a daunting task.

Carbon Copy Cloner Serial Number