Originally published at: Cloudy with a Chance of Insanity: Unsticking iCloud Drive - TidBITS
As with all its services, Apple offers no real troubleshooting when iCloud Drive synchronization stalls in macOS. Glenn Fleishman encountered a problem that took months to diagnose and fix. In the process, he went through the wringer of trying nearly everything suggested online, via Apple support, and from colleagues. In the end, the magic that fixed it was undisclosed engineers.
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Maybe this info should be added to the next edition of Take Control of iCloud.
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I think some of it is, maybe? But I have been talking through it with Joe and Adam as I’ve had these failures, so it will trickle in!
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I had multiple macOS problems with a new M2 Mac mini + Studio Display, though not involving iCloud. Spent hours on the phone with very helpful Apple advisors to no avail then suddenly a couple of the problems vanished. I believe firmware upgrades / macOS updates were involved but no one from Apple communicated what and how. A couple of the Finder issues persist and my own analysis shows that they are related to having more than 10 audiobooks in the Books app (I know, this makes absolutely no sense) – with fewer than 10 books there are no issues, add an 11th and bingo.
I share your pain. I recently rearranged the Safari bookmarks on my iPad Pro—my daily driver—in alphabetical order. (There were finally too many of them to rely any longer on muscle memory to locate them easily.) The change didn’t propagate to Safari on either my iPhone or my Macbook. Now, a month later, after 2 system software updates and five sessions with an Apple senior support specialist—lots of screen sharing, bookmark creation and deletion, log transmitting, etc.—there’s still no solution. the issue remains in the hands of Apple’s iCloud engineers, I’m told, but there’s apparently no projected date as yet for a resolution of the issue. To be fair, icloud has been rock solid for me until recently. From recent eveidence, including this post of yours, it looks to me like iCloud may have finally encountered some serious scaling issues. I so hope I’m wrong….
Hi Glen, a couple years ago, I stopped using my Amazon Glacier for archive and went to iCloud. I uploaded my files from the Safari iCloud interface rather than expecting this work to take place in the background from of macOs. Almost everything went lickety-split. But I did have a hitch as well - and Apple support came through. The issue for me was that the Safari iCloud interface would balk at files larger than 10 GB even though the iCloud handles files up to 50 GB. The 10 GB upload limit turns out to be a hard stop for the Safari iCloud interface. So for the very largest files I had to use the traditional desktop iCloud folder. All of my information is current to my experience in 2021 and maximum file sizes could be different - but the good news is that this is something that Apple Support knows.
I had my iCloud Drive stuck with a 230Gb upload in perpetual never-ever-gonna-upload mode.
Tracked it down, cache files from an errant DevonTHINK database.
Very interesting. This didn’t come up (I keep all my big files backed up on a combination of local drives and via Backblaze) but I like to know these facts!
That’s a lot o’ pain and suffering. Reminds me of the torture of hitting the long-standing and arbitrary 50,000 item hard limit for calendar events, which happened to me twice. When that happens, and it will eventually, all your syncing between calendars grinds to a halt. You will be forced to abandon your entire digital history (or do what I did) and start over again.
Christ, what a complicated process! I wouldn’t mind iCloud Drive being a wee bit temperamental, but the failure modes you describe sound very bad, with no clear and obvious way to fix it, and I think most of us here are fairly well exposed to technical issues to know that beyond a certain point even geeks and computer people can throw their hands up in frustration. It seems to me that, most worrying of all, is the possibility that files can simply just refuse to upload. I mean, why? Why should iCloud Drive even begin to discriminate against a particular file? What strange process makes that even possible? In general I’d say, as someone who uses the feature fairly lightly (about 27 GB total or so, with minimal resolvable issues in the past) that iCloud as a whole is one of the more brittle components in Apple’s ecosystem–that, in fact, I discovered great joy in recently setting up a server Mac without signing into iCloud. That probably says something.
Unrelated: the title bar of my iCloud Drive window has changed to “com~apple~CloudDocs”, for no apparent reason. This is definitely not a sign of bad things to come on this Friday 13 …
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Me too. Oh, look…it’s back to “iCloud Drive” today. Seems to be switching on a slow wave cycle with a period of several weeks. 
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This problem of the iCloud sync is not resolved for systems that have their home directory on an external drive. At this time, there appears to be no fix but to turn off iCloud Drive if you have your home directory on an external drive. Once I turned off the cloud drive, I was able to get the system back up and working. It appears that Apple is not testing new releases with home directories on external drives; this is the second release that has had issues if you have moved your home directory.
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It is ongoing problems like this is why I don’t use iClod and never have trusted Apple to get these kind of online features right. This is just another kind of MobileMe fiasco. I will never trust my data to anywhere except on equipment I OWN.
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I wonder if the clue to this is in your first few statements, quote:
"After deciding to switch from Dropbox to iCloud Drive, I moved a few smaller sets of data to test. Those synced to iCloud Drive fine, so I next moved dozens of gigabytes to iCloud. That’s where the problem cropped up—the number of files left to upload remained unchanged after days.
In my first pass at solving the issue—doing nothing—the problem seemed to self-heal. I assumed it was transient, so I continued my migration, only to see another stall right away. "
My idea is that you first moved smaller sets of data. I think that worked because of size. Then you did larger GB of data, which eventually worked itself out, the buffer finally was able to do the transfer and didn’t report it until the transfer was totally complete… But the clue is that larger sized moves stalled out. Just wondering if you had kept moving smaller quantities of data each day, that the system would catch up? Perhaps the large moves clogged up the system? Just my idea?!
Perhaps the analogy I’m trying to state compares with trying to run too many open programs that are hogging memory and constantly swapping out causing the spinning color wheel. Or, filling a disk nearly full and having problems because there’s not enough room to swap stuff out? Just my idea.
Did Activity Monitor show files being sent? Like trying to fill a swimming pool with a garden hose, something like that?
See the part of the article about trying half and half. I did a whole lotta of staging experiments: moving data back, trying smaller amounts, etc. It would have been another 2,000 words to list all the fine details. But I did wonder if it was something like that.
Eventually for “four months” isn’t exactly the right term, and Apple said it was a problem and they clearly fixed something on their end.
Definitely wasn’t CPU bound, etc. In fact, the weird part, was that most of the time a small number of files (< 200) seemed to cycle through. Sadly, despite all efforts on my part, I was never able to find a “death file” that was killing the process or a set of files. Nor did Apple suggest this.
It was pretty clearly a server-side issue given that months passed and only after extensive documenting and data dumps to Apple was the problem resolved within a few weeks.
Wow, a responce in just an hour or so.
Glad you got the problem solved and thanks for Tidbits. Been reading for years.
The article this time about old age is going to come in handy for a friend and
some for myself. Bookmarked.
Byron
Thanks @glennf for the guide, iCloud troubleshooting was painful - I recall running into sync problems once when I set up the 2019 MacBook Pro 16". I tried the binary search method, but in the end I went nuclear and turned iCloud off then on again. I did not know about the bird and cloudd daemons so that is good to know.
I am not sure if Mother Nature has a problem with all the killings… 
Spoiler: Mother Nature
Refers to a skit performed as part of the iPhone 15 launch video, which got a lot of people talking and some parodies made.
My TidBits mail message disappeared by itself into thin air while reading this article on Sonoma Mail … oh well – good the article was online as I just had another customer with a related iCloud problem. Side note: my preferred way of treating networks is to use ethernet if possible, but keep Wi-Fi on without connecting to any network (as some Apple services wants it like locations services and to keep the clock running correctly) – it also used to be a standard problem for connections to a FileMaker server. Luckily one can now easily choose not to auto-connect to ones local Wi-Fi network … . (Yes, Apple should intelligently manage two active netwrok connections, but who would trust them on that?)
I agree. Apple has never been successful with the cloud. After a few iCloud disasters, I minimise my connections with iCloud.