Target disk mode broken after High Sierra install

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Level 1

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Target disk mode broken after High Sierra install

Two days ago, against my better judgement, I upgraded my Sierra system on my MacBook Pro (2017) to High Sierra because I grew tired of the constant upgrade notifications appearing on my screen. Yesterday I discovered that I could not mount the MBP in target disk mode on my old office Mac Pro (Yosemite 10.10.5, Early 2009). I do this so I can sync files between the systems using ChronoSync. After spending 2+ hours on the phone with Apple support, the conclusion was that the new APFS disk format can not be mounted on the old machine through Firewire. This is extremely distressing, not to be able to access the laptop through target disk mode with a FIrewire cable connection. I was, however, able to mount the disk onto my new iMac at home over my WiFi connection, but my old office Mac Pro does not have WiFI hardware, so I must use a wired connection. There was no warning from Apple that the new disk format would break target disk mode for this system. Does anyone have any suggestions? Is it possible to undo the High Sierra installation?

MacBook Pro TouchBar and Touch ID, macOS High Sierra (10.13.1), Mac Pro (Early 2009, 10.10.5)

Posted on Jan 23, 2018 11:51 AM

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Answer 1

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J. Charles Holt1

Level 2

315 points

Jan 23, 2018 1:33 PM in response to metrologuy

The problem isn't really Firewire so much is that earlier versions of the operating system don't recognize APFS volumes. Unfortunately, your Mac won't run anything newer than 10.11. 😟 Apple has documented this, but you have to know to look for it: How to choose between APFS and Mac OS Extended when formatting a disk for Mac - Apple Support

Apple is pretty good with backwards compatibility—I'm running High Sierra on a Mac Pro from 2010 as I type this—but they can't support legacy devices in perpetuity. It's an unfortunate side effect of having the latest and greatest.

In order to revert, you'll need to erase your APFS drive and reformat it as HFS+, and then restore from a backup.

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Answer 2

metrologuy Author

Level 1

8 points

Jan 23, 2018 1:51 PM in response to J. Charles Holt1

Thanks for the info, which is what I figured it would be. But I feel as if I were snookered by Apple into "upgrading". I don't recall any warnings about changing the disk format. Had I been aware of this, I would not have done it. The only reason I did it was to stop those annoying pop-up notifications to install High Sierra. The diabolical thing is that there is no way to close the notification without opening the app store. A waste of time and effort. Now I am stuck. Thanks, Apple.😠

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