What you need to know about the HFS+ file system, so you can understand error reports and how to repair it using Disk Utility and other tools.
journal
Explains how Time Machine knows what to back up, why it performs deep event scans, and how that system is different from HFS+ journaling.
Your disk’s journal aims to prevent disk errors which can occur after a crash. Here’s how to use it to protect your Mac’s data.
The Eclectic Light Company 