Backup to external drive x2 as mirror copies

I am new to Duplicati and fairly new to backing up data – wish to get better at that though.

I wish to make data backups to external drives for local site storage. So I wish to select main drive data folder and all subs and associated files to be backed externally to plug and play drive – however wishing for a mirror of the same backup to be made to a second drive at the same time to account for external drive failure redundancy.

Is there a way of configuring Duplicati to do this without going to a RAIF1 or 10 solution?

And if not - is a RAID software controller solution feasible re ease of setup? I am attempting to keep budget reasonably tight.


You use the phrase “second drive”, but I think you mean that the “first drive” is your normal drive with your data, and your “second drive” is the one backup drive. You want data backed up twice onto the second drive? You also said this was a “plug and play” drive, so I’m guessing this drive is something you plug in, then go to Duplicati to back up, then you unplug?

I would just configure two separate Duplicati jobs. Trying to keep them perfectly mirrored as one backup job is tricky. For example, if a file backup to backup spot #1 works but backup spot #2’s backup fails mid-upload, now backup spot #1 is different than backup spot #2. Now you don’t just have a backup problem, you have a replication/syncing problem. That’s a nightmare to have any program try to solve in a single backup job. For that reason, two separate Duplicati jobs are the best option.

If you are plugging in the drive, backing up, then unplugging, then you could configure Duplicati to run a script when the first backup completes. Upon backup completion, have a script sync all files from your first backup to the second backup.

If you want to do this automatically, as you said, I suppose a RAID 1 on a single drive could work? But honestly, you are far more likely to experience full drive failure than you are to experience a bad sector on a drive. If you are feeling the need to have two backups, I’d honestly just use two separate backup drives.

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Based on that, I’m going to make a suggestion.

Is there a good reason you’re using a program like Duplicati and not something that can maintain a simple copy of your data folders?

Examples of good reasons might be if you need your backups to be encrypted (because the backup drives might be stored in an insecure location) and you want to keep many past versions of files.

In a disaster or crisis, it’s much easier to restore from a backup that’s just a simple copy of your file system. As an example, FreeFileSync can copy only the files that have changed and keep old versions of the changed files, and it runs on Windows, macOS and Linux. It can even copy to SFTP or Google Drive. However, it doesn’t do encryption or deduplication, and it always copies changed files in their entirety.

(I use FreeFileSync for my local backups, and for a few things to SFTP and Google Drive that don’t require encryption or deduplication. For local backups that require encryption, I use a VeraCrypt container to create the virtual drive that holds the backups.)

Instead of duplicating the backup on both external drives, consider alternating your backup drives; that is, each backup goes to the opposite drive as the last one. That way, if something goes horribly wrong during a backup, you still have the backup on the other drive. Weigh the risk of a catastrophic failure during backup or inadvertent introduction of malware you haven’t yet detected on your computer into the backup against the risk of having to use stale data if both your computer and the most recently used backup drive fail.

This is just my opinion: Though Duplicati can be used for local, on-site backups, I think it rarely should be. It’s optimized for situations where minimizing data transfer and storage while maintaining end-to-end, client-side encryption are essential, which is typical when making cloud backups. It’s an unnecessarily complicated solution for most local backups, where keeping things as simple and robust as possible is likely to be worth the cost of a little extra backup time and storage.

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A single Duplicati backup goes to only one destination, however @brad and @Coises have great ideas.
There are a lot of things that factor into the best approach for a situation, so maybe needs can be clarified.

Are you sure you don’t want a remote backup to protect against disasters that also destroy local backups?
Keeping two backups (maybe done differently) is probably safer than a single backup. Backups can break.