Odd Phenomenon With DMG Archives and iCloud

TidBITS Talk
1

This is weird.

I have a .dmg file in which I store docs. I have moved a folder into the dmg archive, let’s call it Old Tax Docs 2024. I drop the folder in, check the content, let’s say the folder has three sub folders totaling 250 mb. So then I make a copy of the dmg file and rename it, check it, all good. Then I move the renamed dmg to my iCloud folder, check it on the computer I am working on. All good 250mb.

Next step, working from another computer go to open the archive and lo and behold the folders recently moved exist, but they are Zero mb of data, they are shaded and empty, and not openable

Something weird is going on. How did iCloud erase the contents of the interior of a dmg archve

boggled

2

Did you just peak in Finder or did you try to mount the DMG onto the other computer’s desktop. My first guess is that it didn’t download the DMG to the other computer and on this computer it is Zero. You are not looking at iCloud, you are looking at what your machine has from iCloud.

1 Like
3

Now that I have rechecked, and reattempted another upload, I think the issue is that the updated archive file never actually synced. … I have no idea why the file I thought I had uploaded the other day had only grayed out empty versions of the folders I added. … I started thinking permissions issue, but I think the upload never synced

Further odd anomaly. The file which I ended up uploading to my Google Drive in 2 minutes, is still uploading to iCloud after 3 hours. I can access the iCloud version of the file from the original computer, but it has not shown up as synced yet on anther computer at work.

Here is another super odd thing: looking at the progress bar activity it took an hour to gauge up to 65 mb of the 1G file, then it blipped randomly up to 300 mb of the file, and then, an hour later it was retrograded back to 65 mb of a 2 Gb upload … I guess I just don’t understand iCloud logic. So, I guess it’s never going to sync. I just download the file, from Google Drive, at the work computer in way less than the original 2 minute upload from home

#Sheesh

4

Is your DMG drive a Apple Sparse Image format? This is the new format that implements its sparseness using APFS.

If so, I believe that when it syncs to iCloud it occupies its maximum allocation size. And same when it gets synced from iCloud to another machine.

So an Apple Sparse Image .dmg with a maximum size of 100 GB will upload 100 GB to iCloud, even if it only contains 250 MB of data.

If that’s your situation, I’d advise using the Sparse Bundle Image format instead.

Non AI slop reference: How robust are APFS clone and sparse files? – The Eclectic Light Company

1 Like
5

Another possible factor: certain I/O processes—such as Time Machine backups—are treated as low priority by macOS.

I haven’t tried this “stop deprioritizing Time Machine” Terminal command for a long time but I picked it up on a support forum somewhere (maybe MacIinTouch when it still had message boards:
sudo sysctl debug.lowpri_throttle_enabled=0

Perhaps it would have an effect on iCloud syncing.

6

a run of the mill, I suppose: Disk Image Volume • Mac OS Extended (Journaled)

7

I am beginning to think that the throttling partially involved is my home internet but with the exception that even at half the spec’d lowest upload speed the file should take no more than a minute or two.

I just uploaded the file to my iCloud being at work … took about 25 second to start > slight pause > then swoop there it is

8

Regarding I/O processes, wouldn’t drag and drop method sort of override the typical low-priority processing for recurring backup protocols? Just wondering