# ZFS overlay



## tOsYZYny (Sep 15, 2020)

I would like to sync my photos with Google Photos using their sync utility (Windows / MAC) as I have quite a bit of photos.  All of my media is stored on a ZFS volume and I generally make it read-only after I update it (to prevent data loss).

I came across unionfs, but have read that it is not advised to use it for writeable data due to data loss.

While I do snapshot my media (and do), I would prefer not to:

1. take a snapshot of my media
2. make my media read-write
3. upload to Google
4. revert to the snapshot before
5. repeat

From a trial run, I see that Google's uploader appears to create an upload and download file for each file I want to process.  Which, at that rate would fill up my hard drive.  Furthermore, if I use the steps listed above, there will be a huge amount of data that needs recreated each time.  So, ideally, what I'd like to do is use an overlay where Google's data is stored off the main filesystem from my media all-the-while Google is happy because it can write to the files and do its thing.

However, the unionfs doesn't seem to be production-ready, so what else can I do?


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## tOsYZYny (Sep 15, 2020)

nullfs gives me a writeable layer, but I need the original read only part:

1. read-only volume / mount-point
2. read-write volume / mount-point
3. final volume / mount-point used by Google to upload photos and videos


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