How to Copy Large Amounts of Data in OS X

One of my primary external hard drives is starting to fail. It's the drive I use for almost all of my media, including my iTunes library and probably most importantly, my Lightroom photo library. I decided to upgrade my 3TB drive to a MyBook Duo 8TB to get a high-capacity, mirrored-drive setup.

In doing so, I had a small problem: I needed to copy over 2TB of data to this new drive. If I used the Finder, any hiccup along the way would require me to restart the process. For smaller amounts of data, I would just copy individual subfolders, so if one failed there'd be less to copy. That. Is. Tedious.

After some research, I came across this brilliant, safe, and most importantly, fast method: use rsync! When in doubt, turn to the terminal, right?

I ran this command on my top-level folders to copy from the old drive to the new:

sudo rsync -vaE --progress /Volumes/SourceDrive/TopLevelFolder _
/Volumes/DestinationDrive

A few notes to point out, since I made a few mistakes that weren't readily apparent in the StackExchange answer:

• Your destination path should be the folder that you want to copy into. In my first copies, I included the destination folder name I expected, so my path ended up being /Volumes/DestinationDrive/DestinationFolder/DestinationFolder.
• No trailing slashes!
• This is a long process. The beauty of rsync, though, is that if it fails you can resume it! This actually happened to me, since OS X decided to disconnect the drives in the middle of the night. All you have to do is run the exact same command again and it'll pickup where it left off after doing a quick scan.
• You can run multiple jobs at a time. Just open multiple terminal windows/tabs and run the command again.
• For a more in-depth explanation on each of the rsync flags, refer to the AskDifferent StackExchange answer.

I hope this helps you as much as it helps me. Happy copying!