Maintaining a clone backup of your startup drive is a good idea. An essential idea, if you want to survive a potential hard drive disaster with a minimum of fuss. But even a great idea can occasionally result in frustration. With backups, the frustration can come if some software on your drive is unable to figure out that your startup drive and its clone are two different volumes.
It's an understandable error, as the whole point of a clone is to be "identical" to the original drive. That's why, as in an example I previously covered, Spotlight can become confused and start indexing a cloned drive, even if you've selected to exclude it.*.
More recently, I had another clone-related hassle. This time it involved Backblaze, the software I use to backup my files to an online site. When I first started using Backblaze, all went smoothly (I've described my experience in more detail here).
A few weeks ago, however, I began getting alert messages stating that "Backblaze is not able to back up one of your hard drives." The drive in question was a clone, a drive that I had never requested to be backed up in the first place. Apparently, Backblaze was getting confused about clones. But why was this alert popping up now, after weeks of smooth sailing?
I contacted Backblaze support for answers and learned that the company had recently upgraded its software. A key change in the update was that Backblaze installs an invisible .bzvol directory at the root level of selected drive(s), so as to better "identify" the drive. The alert message appeared because, after this directory was copied to the clone drive during a normal backup, Backblaze mistakenly assumed that the clone was supposed to be backed up, even though I had not selected it.
Happily, the problem has been addressed. For starters, Backblaze has further updated its server-side software to handle this situation more gracefully. However, you still need to do a bit of work to get everything working smoothly:
- Download and install the latest version of the Backblaze client-side software via the link on this Backblaze page.
- Create either a blank file or an empty folder, name it "bzstop_clonewarn," and place it in the .bzvol directory on your original drive. To get inside this otherwise invisible directory, select the Finder's Go to Folder command and type: /.bzvol. If you use SuperDuper! or Carbon Copy Cloner, you can instead create a script to exclude the .bzvol directory from your clone, as cited on this Backblaze page.
I have taken these steps and can confirm that the alert messages no longer appear. Problem solved.
That said, I remain a bit critical of Backblaze. First, the company updated its software in a significant way, without any user notification. Never a good idea, especially for backup software.
Second, the instructions on how to fix the problem are not as clear as they should be and may include errors. For example, it doesn't seem to make sense that you can install the bzstop_clonewarn item on the clone drive rather than the original drive, as it will be deleted after the next backup. Yet, Backblaze's instructions state that you can install the file on "either of the two identical drives."
Finally, you'd be hard-pressed to find this information on Backblaze's site. For example, to find the page with the bzstop_clonewarn instructions, you have to click the "How it Works" link on the home page, scroll down to the section that says "External Drives," click the "Read more" link, scroll down to the bottom of the FAQ list that appears, and select the "Read more information..." link. Backblaze should do a better job of helping users find this fix.
* A well-designed backup utility solves the Spotlight hassle. I now use SuperDuper. This utility preserves a separate Spotlight index state on the clone, rather than simply copying the state from the original. As a result, Spotlight ignores the clone.
This story, "Bugs & Fixes: Winning the Clone Wars" was originally published by Macworld.