2017 27" iMac booting from External Thunderbolt SSD Issues

[Chris1001]

Hi,
About three weeks ago I installed Monterey on a Crucial 2TB SSD in a Sabrent Thunderbolt enclosure. I fresh installed all my programs to ensure it was was as clean as possible. This took me a bit longer than I thought it would but everything (or so I thought) had gone well.

The iMac had an internal 3TB Fusion drive which was working well, after about a week of testing I split the Fusion drive into separate drives to be used as additional storage if required.

Unfortunately I have not been using the iMac for any lengthy periods until yesterday... When the issue first raised its ugly head.
After going out I returned to find the iMac had shutdown on it's own and refused to restart. Only after removing the power cord would it restart but I got no error messages when it booted up. Wishful thinking I know but I thought it might have just been a 'one off'. How stupid to think that and of course the problem has returned.

I have reset the SMC and NVRAM but it has made no difference. One question here? The guidelines say to remove all external connections when performing these resets, would that also include the external Thunderbolt drive which has the operating system on it?

Another issue has also appeared. When I shut down normally everything is fine, but on startup I now see the error message: "your computer was shutdown because of a problem". I am not aware of any problem and in the past I have only rarely seen this message when the computer has locked up and I have shut it down by holding the power button in.

I am struggling with this one... Does anybody have any ideas on what might be wrong or point me in the direction of additional testing to assist in identifying the issues?

Thanks in advance,
Chris

 

[Tdude96]

on startup I now see the error message: "your computer was shutdown because of a problem".

I have a 2017 27" base model that I'm using an external thunderbolt drive for. Sounds like the main differences between our setups is that mine is a base model, and I didn't touch the fusion drive, I've left it as a backup just in case.

The thunderbolt drive configuration has worked fine since early this year when I made that change. But last week I started getting this problem. In addition to that message, no menu bar would show at the top of the screen when I logged back in after a restart.

I went through the same troubleshooting steps you have, but after reaching wits end on that, did a web reinstall of Monterey (not a full wipe, just a reinstall of the OS on the TB drive). So far 🤞 the problem hasn't come back.

 

[Chris1001]

I have a 2017 27" base model that I'm using an external thunderbolt drive for. Sounds like the main differences between our setups is that mine is a base model, and I didn't touch the fusion drive, I've left it as a backup just in case.

The thunderbolt drive configuration has worked fine since early this year when I made that change. But last week I started getting this problem. In addition to that message, no menu bar would show at the top of the screen when I logged back in after a restart.

I went through the same troubleshooting steps you have, but after reaching wits end on that, did a web reinstall of Monterey (not a full wipe, just a reinstall of the OS on the TB drive). So far 🤞 the problem hasn't come back.

Thanks for the reply. I have now seen that problem of the top menu bar disappearing. Also it is taking 3 or 4 times as long to boot up. Every time I switch the damn thing on there seems to be a new error...
I'll see if any more replies come in offering help but I wanted to avoid a reinstall after spending so much time on the fresh install.
At least I have one possible solution that was successful in your case.

 

[EugW]

Something on your drive probably got corrupted. I had this same issue in Monterey on an internal NVMe SSD on my 2014 Mac mini after a bad shutdown. I couldn't fix it even from Time Machine backups. I ended up having to reformat the drive and now it runs fine.

Why aren't you using the internal 128 GB SSD for your Monterey install anyway?

BTW, while I've never owned a Thunderbolt enclosure, I've occasionally had issues running off external DIY drives using 3rd party bus-powered enclosures (USB and FireWire 800). I get the impression that the power regulation of some of these things isn't always the greatest (or maybe it's a combination with issues with certain Macs)? Specifically, I've noticed that 3rd party DIY drives that used external power are more consistent than 3rd party DIY bus-powered drives. In fact, I had one drive that usually worked well with bus-power but 0.1% of the time didn't. However, once I plugged external power into it (as it had a DC power jack), it worked 100% of the time. OTOH, well-respected name brand external bus-powered drives tend to do better, since these are specifically designed to run off bus power.

 

[Chris1001]

Something on your drive probably got corrupted. I had this same issue in Monterey on an internal NVMe SSD on my 2014 Mac mini after a bad shutdown. I couldn't fix it even from Time Machine backups. I ended up having to reformat the drive and now it runs fine.

This confirms what Tdude96 said, it is looking like a reinstall of some type will be required. Very disappointing because this has been a complete fresh install and my fear is that the issue might return. Also I have not been able to identify what has caused the problems. Having Covid which I caught from my parents and started over the weekend has not improved my detective skills!

Why aren't you using the internal 128 GB SSD for your Monterey install anyway?

Good point but it was not large enough for what I wanted. I run a Parallels Windows installation and having everything on the external 2TB drive made sense.
I had hoped to change the iMac this year but like many I was devastated the 27" version was not updated. I don't want to move down to a 24" machine. That is the reason I decided to try running the iMac of a thunderbolt enclosure, speed it up a bit and hopefully a larger iMac will appear next year.

BTW, while I've never owned a Thunderbolt enclosure, I've occasionally had issues running off external DIY drives using 3rd party bus-powered enclosures (USB and FireWire 800). I get the impression that the power regulation of some of these things isn't always the greatest (or maybe it's a combination with issues with certain Macs)? Specifically, I've noticed that 3rd party DIY drives that used external power are more consistent than 3rd party DIY bus-powered drives. In fact, I had one drive that usually worked well with bus-power but 0.1% of the time didn't. However, once I plugged external power into it (as it had a DC power jack), it worked 100% of the time. OTOH, well-respected name brand external bus-powered drives tend to do better, since these are specifically designed to run off bus power.

It's my first time running the operating system from an external hard drive and so far it's not been very successful. The problem I have is I don't really have the skills to delve deeply into what the issues might be. I see Ventura was released today...If I was really brave I could update to see if that cured the issues? I never normally update until .2, let the bugs be identified by the early adopters. I will install Monterey 12.6.1 to see if that helps but I am almost certain it won't. Updating rarely if ever shorts out issues, certainly not in my experience.