If you have to copy a large amount of data, say 15TB from one hard drive to another, the finder is not your friend. The way the finder copies data allows for disk errors or I/O (in/out) errors to fail the whole copy. For example, if you've been running that 15TB copy for a few days and it fails with an error at 99%, you're screwed. Using the terminal to run an rsync command is ideal, it copies files bit by bit, safely, and if there is a problem (disk disconnected? power outage?) run it again and it'll start off where it left off. Sweet.
*If the copy is interrupted for any reason, run the same command again.
For advanced rsync commands CLICK HERE
For example commands to exclude files and folder from an rsync copy: CLICK HERE
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