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
We're some guys and gals in San Francisco who fix macs. We can remote in and help you with stuff. It's like our job or whatever.
(five one zero) 761-6559
**We charge $1.28/minute for quick fixes.