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I recently have a large amount of data I needed to upload into Google Drive. I decided to use Disk Utility to create a container for it (otherwise Google Drive would have to create many files and directories taking up a huge amount of the time).

I noticed that Disk Utility creates a read-only DMG file by first creating a sparseimage, then converting it to a DMG file.

As a result, to cut down on time, I am wondering if creating sparseimages of my files, then uploading to Google Drive is better than putting it into a DMG file. My two main concerns are:

1) I read somewhere that sparseimages seem to have a greater than of being corrupt on Google Drive or cloud services?

2) Is there any real difference between the two beyond write/read-only capabilities?

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From Wikipedia:

A sparse image is a type of disk image file used on macOS that grows in size as the user adds data to the image, taking up only as much disk space as stored in it. Encrypted sparse image files are used to secure a user's home directory by the FileVault feature in Mac OS X Snow Leopard and earlier. Sparse images can be created using Disk Utility.

Unlike a full image file (.dmg), which takes up as much actual space as the real disk it represents (regardless of the amount of unused space), a sparse image file (.sparseimage) takes up only as much actual disk space as the data contained within, up to a maximum of the capacity assigned during creating.

https://en.wikipedia.org/wiki/Sparse_image

In your case, because you don't indicate you plan to use the utility of the sparseimage mechanism in any way to create an expansible, or 'live' storage container, creating .dmg files would be called for because they are monolithic files best use for archiving.

If the data is already indexed or organized in some way, then creating separate .dmg files make a logical container to extend and reinforce that organization. Ex: TaxDocuments2010.dmg, TaxDocuments2011.dmg, etc.

Google has a max size of 5TB per single non-Google document file, BTW.

Lastly, you may wish to package this data in a non-Apple proprietary format such as tar or GZIP so it can be opened on other platforms.

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  • Does tar,gzip differ much from a DMG file? Would hard links be kept? Which one would you recommend?
    – user321627
    Sep 21, 2017 at 2:24
  • @user321627 - I leave that for you to experiment with, as only you can make the final determination which is best. Consider the expected longevity of the archived data you wish to keep. Future ability to unpack (and decompress/decrypt) the files is crucial. Apple software will be around for a few years at least, so the .dmg format most likely will be supported. Depending on the importance of the data, you might also want to consider archival storage of the .dmg files on Dropbox and Amazon AWS in addition to GDrive to have a triple cloud backup.
    – IconDaemon
    Sep 22, 2017 at 1:09

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