If anybody ever says that Apple is a lot better than Microsoft one thing that they need to pay attention to is the fact that both companies are guilty of the same problems. In this case I’m talking about both companies habit of letting long standing regressions in their software languish, unaddressed for long periods of time. Apple’s sin in this case is with Disk Utility. Apples has allowed a bug in the Disk Utility in macOS go on, unaddresses since about OS X 10.13 or so when they changed the structure of Time Machine Backups to force an encrypted drive. I’ll admit that I’m not being completely fair. I’m running an older version of macOS on my laptop so this bug may indeed be fixed but it still stayed in the software for a good 3 years.
By trying to make it easier to use an encrypted volume for backups Apple has added a few steps to the process of checking these volumes for structural errors. This means the graphic Disk Utility frequently false positives, saying that your volume has a problem. The real issue is that Disk Utility hasn’t properly set things up for the volume check to happen. Back in the olden days, UNIX you wouldn’t let you use a Volume with structural problems because you couldn’t mount it with write allowed. Today is you can mount broken drives in write mode. Then you get to cross your fingers that you’re not compounding an existing problem. Side note: Here’s where I admit to being really really old because 99% of the time its actually okay and that’s actually the case. The result is that Disk Utility can’t properly check out your Time Machine Volumes. To check one out you need to take the time to boot your machine into recovery mode where all of this shiny that makes users happy is disabled. In recovery mode, Disk Utility just works. Compounding this problem, when Apple does the check from a normal boot, it doesn’t detect its own bug and declares that your volume is dangerously corrupted and unreliable so your best best is to start from scratch. This article shows how you can at least get some peace of mind by checking the state of the volume and repairing it from the command line in a terminal window. I would’ve liked to have seen a screenshot of the command line session. But the author decided that figuring out which disk you need to check is too difficult and they didn’t include one. That’s the responsible choice since you are going to be doing a lot of potentially destructive commands with sudo. I worked my way through the process on my own third Time Machine Volume. I have this issue because this Volume is connected to my docking station. It auto mounts when I use my machine on my desktop so I can have a full sized monitor. It’s easy to forget that the Volume needs to be ejected cleanly and quiesced before I disconnect from the docking station. I’m cultivating the habit of ejecting this Volume when my backup has completed.