Backing up - DMGs or 100s of small files?

I have a number of collections of files. Some of it is old downloaded courseware (hundreds of small MP3s, a couple MP4s, JPGs, PDFs, etc.), some of it is just old customer data (old WordPress website directory trees that I don’t want to delete for archival purposes, PSD files, etc.).

Since the backup agent (any agent - although I use BackBlaze at this point) typically has to scan through individual files, and since there’s some overhead with that scanning (including maintaining an index of all these files!), would it be more efficient to package up some of this old data that doesn’t change as DMG files, or sparse images?

In case it matters, my backed up file count is close to 5 million files. So this isn’t a small issue - lots of that could be converted to images.


I would keep it as individual files to make it easier to find the file you’re trying to recover in the future.

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Why not just backup to an encrypted sparse image? You can keep the structure intact and securely backup your data

You might consider archiving some of these files (i.e. creating zip files), especially if they’re more for archival purposes and if you’re unlikely to be searching for individual files.

I use an encrypted sparse image for sensitive information (e.g. tax returns) to add another layer of security.

A word of warning: Backblaze excludes disk images by default. You need to manually remove them from the excluded list before they’re backed up.

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I need to send this stuff off-site for redundancy purposes, hence Backblaze. And that’s basically the question - should I use disk images for local storage, and have Backblaze back those up?

Thanks for the warning. Nothing quite like coming up with a backup plan and discovering that things aren’t actually being backed up. :smiley:


Diffchecker algorithm scans don’t take that long. Backblaze spends proportionally much more time actually transferring files for backup. I wouldn’t worry about it.

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I do essentially the same thing. Mount a dmg/sparsebundle - backup files - unmount -> send to off-site backup (synology C2 in my case) Gives me double safety

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