Earlier today, a client’s hard drive exhibited an “invalid node structure” error after I ran Repair Disk in Disk Utility.
Browsing the tech blogs, it appears that this error is an indication that the drive is on the verge of failing and should be replaced ASAP. Both Disk Warrior and Tech Tool Pro noted errors with the startup drive and could not correct the problem. The boot drive installed in the client’s PowerMac G5 is the original device that is now over 5 years old, which is about the time when drives start to fail. I advised my client to buy a replacement hard drive tomorrow, and I will endeavor to recover as much data as possible from the original drive. For reasons unknown, the software program that was supposed to regularly back up the user’s files onto a secondary hard drive had not been activated for 2 years. If the data is unrecoverable, then his only recourse is to use a data recovery service like Drive Savers.