Then, I’ve looked at pricing of cloud storage providers, such as AWS, Azure and Google Cloud. Those offer storage around 1 cent ($0.01) per GB per month. That’s a quarter of the OneDrive cost! It’s even less if you consider their archive offerings (AWS Glacier, Archive in Azure, Coldline Storage for Google). The cheapest offering here is from Microsoft at 0.2 cents ($0.002) per GB per month, but with some usage caveats. Since the point of backups is to keep them for a long time, this quickly adds up though.

Now I’ve written a line or two of code before, so I figured I could as well write my own tool for this. So here is bart, the backup and restore tool. Note that at this point I do not offer bart as a ready-to-use executable, but only as MIT-licensed source code. In addition, bart currently works only with Azure Blob Storage – or with storage mounted into the machine’s file system. However, adding other cloud providers/archive destinations should be relatively easy, given the interfaces used in the tool.

Security

In terms of security, bart encrypts every file before storing it in the archive destination. A user-provided password is used together with a randomly generated salt to derive a key for encryption with AES. On first use of any archive destination, bart generates a random salt, and each archive has its own password and salt. To avoid anybody with access to the archive destination from even snooping the names of your files, the names are hashed (SHA1) and the hashes used to store the encrypted files. This has the disadvantage that renaming/moving a file results in another file in the destination archive, though.

Usage

Once you compiled bart, you can use it as follows.

./bart [-name string] [-path string] [-m noop|restore|delete] -acct string -key string
  -name string
        The name of the backup archive. (default "backup")
  -path string
        The path to the directory to backup and/or restore. (default ".")
  -m string
        A behavior for files missing locally: 'noop' to do nothing, 'restore' to restore them from the backup, 'delete' to delete them in the backup archive. (default "noop")
  -acct string
        The Azure Storage Account name.
  -key string
        The Azure Storage Account Key.

Sources

The sources are on GitHub @ https://github.com/rokeller/bart.

Conclusion

I’ve used bart for backup of some photos/videos for a while now. For the about 42GB I have uploaded so far my monthly bill from Microsoft is about 42 cents ($0.42). Those months where I upload new files the cost is a little higher (a few cents usually) because of the extra transactions. My backed up files are encrypted. If this isn’t cheap and secure cloud backups, what is?

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