Partition won't unmount for verification

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Partition won't unmount for verification

I re-partitioned the Apple SSD in my Mac Pro 6,1 (cylinder) a couple of days ago (the macOS partition was 85% full, so I wanted to enlarge it and to reallocate space in the other partitions). Since then, I am unable to verify one of the partitions (my documents) with Disk Utility or TechTool Pro because they cannot unmount the partition. I can write to and read from it with no problem. The two other partitions (macOS partition, and one where I keep software installers if needed) have no problem with verification unmounting. The partition scheme is GUID. The partitions are formatted HFS+ (Journaled). I'm running High Sierra but don't want APFS since it would (reportedly) slow my backup HDDs to a crawl.

When I force eject the partition in question, Disk Util says it's OK. After remounting, it backs up fine with SuperDuper. The backup copy verifies without protest. Terminal reported unmounting was "dissented" first by Avast daemon (antivirus) and later by AssetCache. I turned off asset cacheing, and briefly disabled ransomeware protection in Avast Premium Security. Neither resolved the problem.

I'm thinking it might be best just to delete the problem partition, create a new one, and copy the content over with SuperDuper, but that may be too drastic. Any ideas, please?

Posted on Jun 25, 2021 2:47 PM

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Answer 1

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scott01 Author

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Jul 4, 2021 11:13 AM in response to scott01

FOLLOW-UP: Problem seems to be solved. I moved AssetCache to the macOS partition, then basically took a shotgun approach: I'd already turned off content caching in System Prefs, but assetcache process was still interfering so I deactivated it in Terminal for good measure, set the cache size to the minimum, turned off "share Internet connection" and specified "only iCloud content" to be cached (since I don't use iCloud). Disk Utility now verifies the macOS partition without protest. Doesn't unmount it, of course, just "freezes" it momentarily. I don't really need content caching anyway.

Thanks to all who replied!

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Answer 2

Jun 26, 2021 12:22 PM in response to scott01

Hey, scott01, you strike me as a bit of a hobbyist, which I think is awesome.

As you know, with HFS formatting, all of the data on the drive is dependent upon a valid drive directory and partition map. If you damage either, then things get ugly. To change a single partition you have to change the partition map which puts all the data in jeopardy.

With APFS, all the volumes dynamically share the available drive space, and if you want to change the size of an existing volume, only that volume needs to be addressed, not the map of the entire drive. And it's easy to do with a single-line Terminal command.

APFS is a really interesting advance in file management. When you have time, I'd suggest you get your hands on a spare SSD and play with it.

Meanwhile, re: your OP... "I'm thinking it might be best just to delete the problem partition, create a new one, and copy the content over with SuperDuper, but that may be too drastic. Any ideas, please?"

You've ID'd AssetCache as the likely culprit here. I don't know about disabling it, but at this point I do think it would be easiest to simply repartition that drive and be done with it. Copy your data from the backup and you're probably golden.

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Answer 3

scott01 Author

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Jun 25, 2021 3:36 PM in response to scott01

UPDATE: Just tried again via Terminal, and it again reported AssetCache as the "dissenter" for volume dismount. Even though Content Caching is turned off, I went to System Prefs and moved the content cache to a different partition. Now the previously unmountable partition unmounts and verifies, the partition that's the new location of the content cache doesn't. When I use Activity Monitor to terminate AssetCache, it just comes back and has no effect on the behavior. Short of turning off Content Caching, which apparently does nothing, how do I get permanently rid of it?

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Answer 4

Jun 25, 2021 3:37 PM in response to scott01

Hello, scott01.

I don't have a particular suggestion to fix your problem, but I just want to throw this out there:

One of the best advantages of the APFS format is the ability to add, delete and resize volumes without having to mess with other existing volumes. It really takes the headache out of the process you're going through now.

As for the HDD slowdown that you mention... I don't see any slowdown on my iMac 2013 Catalina w SSD internal startup and HDD external TM backup drives.

IMHO, I'd go ahead and take that plunge. Embrace the new tech. With your hardware I think it would be a breeze to roll up to Mojave at least, if you still rely on 32-bit stuff. Eliminate this particular headache going forward.

Out. 🙂

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Answer 5

scott01 Author

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Jun 26, 2021 10:11 AM in response to D.I. Johnson

Thanks, D.I. Good to know you're not seeing HDD slowdowns with APFS. I don't embrace new tech easily, unless forced to.

The repartitioning process was not problematic, and the partition content did not change; just the available space. That's why I don't understand the sudden appearance of the unmounting/verification issue. I did rebuild the volume directories on the HDD backup before copying back over to the SSD, so don't know if that could have introduced the issue.

Perhaps I should move the AssetCache to the macOS partition, but being unable to verify that partition would be a bit scary.

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Answer 6

scott01 Author

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16 points

Jun 26, 2021 1:24 PM in response to D.I. Johnson

Thanks, D.I. I did verify the partition map with TechTool Pro before and after the repartitioning. The problem seems to be with where the Asset Cache is located, since moving it to another partition transferred the unmounting issue there -- even though the Asset Cache has seen little to no activity in the past week. I'll keep poking around in the forums and knowledge bases to see if I can find out why this should be.

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