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I've been using Google Drive to backup via Time Machine on a macOS 10.13.6. More precisely, I've created a sparse bundle disk image, attached such image and mounted it in order to make it visible to Time Machine.

Now, usually Time Machine finishes the backup way before Google Drive completes syncing all the files. Occasionally, however, either my computer sleeps or due to other reasons my internet disconnects. Or, maybe worse, due to power outages, my computer might eventually turn off. In those cases, what happens to whatever is being written inside the disk image?

Usually, when the internet disconnects and reconnects again (even after several hours), Google Drive seems to indicate that the progress could be resumed. At least, I see some files similar to the ones when Time Machine output was being uploaded. However, I'm unaware on whether some of these files were corrupted or, even, whether all the written files were uploaded.

So, in summary, after creating a file inside the Google Drive folder, for how long and how much can Google drive stores the files locally before uploading then with and without internet connection? nce.

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    This site works better with only one question per post, I've removed the extra question.
    – nohillside ♦
    Commented Dec 15, 2021 at 6:45
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    Also, the setup as such seems to risky. If your drive fails after a TM backup but while Google Drive has partially synced the sparse bundle, you loose access to your whole backup.
    – nohillside ♦
    Commented Dec 15, 2021 at 6:46
  • @nohillside All the questions are intrinsically connected (the general mechanism behind caching and uploading in Google Drive). I'm not aware about the policy here. But in other StackExchange sites, that seems to be ok. I can ask other question anyway if needed. About the safety, that's my unique free unlimited space option now besides an additional physical external hard drive. So I have to live with that.
    – user40276
    Commented Dec 15, 2021 at 6:57
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    I strongly recommend to get an external drive. A backup solution which depends on the main drive not failing while data is getting synced to a cloud storage is no backup solution at all.
    – nohillside ♦
    Commented Dec 15, 2021 at 7:06
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    This sounds like an extremely risky setup that will probably fail exactly when you need it. You're hoping that TM and GD do things in a particular order, and you've got flaky internet connectivity. Have you tested that all your data is intact and can be recovered? Ask yourself 'what happens to my data when any point in the system breaks'. E.g. what happens if your local storage fails during a sync. And how long will it take you to restore all your files over the air?
    – benwiggy
    Commented Dec 15, 2021 at 10:56

1 Answer 1

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As it was mentioned on a couple of comments to the question, saving a file to a Google Drive folder while being offline is risky because Time Machine doesn't backup the Google Drive for Desktop cache by default. The safest way to proceed while working offline is to save the file to a local folder then when going online again move the file to the Google Drive folder.

NOTE: At this time I don't know how to make Time Machine to backup the Google Drive for Desktop cache.

Google Drive for Desktop stores the files as long as it's necessary while it's installed on your computer, just don't keep your computer without Internet connection for a very long time (several months) as Google is continuously updating it and if the installed version becomes too old it might not be able to communicate to the Google servers.

NOTE: I'm returning to Mac after several years so I'm not sure about the specifics about your operative system version, but according to System requirements and browsers it's the oldest Mac version supported, so there is a risk that in the upcoming months it might become unsupported.

According to a couple of answers to Can you back-up your Google Drive folder (on my Mac) with Time Machine the cached files aren't backed up by Time Machine by default.

You can learn about some technical stuff about Google Drive for Desktop on the help article pointed to Google Workspace administrators: Configure Google Drive for desktop

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  • Thanks for the last link. It seems that the cache is capped at 20% of the free space. That might be a problem in my case since stored cached data will likely exceeds that when backing up external drives (way bigger than my internal booting drive). Now, what happens when one exceeds such limit? Will any alert message shown up? Maybe would you happen know a way to force a higher cap? By the way, I don't have any Google .plist file set in the folders as mentioned in Host-wide and Override, so I guess I need to create files there. Still, will Google Drive find them in the path?
    – user40276
    Commented Dec 15, 2021 at 5:40
  • From the second link, relate to the cache is capped at 20%...: "The setting does not apply to files made available offline or files that are in the process of uploading." Regarding the other questions, I suggest you to post a new question.
    – Rubén
    Commented Dec 15, 2021 at 6:17
  • Yes. I've read that. I however don't know enough about Google Drive's algorithm in order to understand where exactly in the code this limit is set. One might be able to bypass it. Also there's another problem that was not mentioned in your answer. The disk image might unmount. What Google Drive will do when it caches a file pointing to a non existent volume? Maybe that's trivial. I don't know...
    – user40276
    Commented Dec 15, 2021 at 7:10
  • I updated my answer. While the original intention of this update was not to address your last comment, IMHO opinion the best advise is the same, while working offline save the file to a local folder then when going online move it to the Google Drive for Desktop folder. Regarding where in the code something is done / the algorithm as the code is not open-sourced only Google engineers are able to answer that and you can't rely on what they say about that for end-user long term decisions as Google make changes to their not open-source code and algorithms without announcing those changes...
    – Rubén
    Commented Dec 15, 2021 at 16:55
  • ...; the release notes doesn't include those details.
    – Rubén
    Commented Dec 15, 2021 at 16:56

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