Evaluating Duplicati to replace Cobian

I have been following backup solutions for many years and this seems to do what I need. I currently use Cobian on W10. I am considering changing my Windows email from LiveMail (which has not been supported for a long time but can still be downloaded if you search hard enough) to Thunderbird but, unlike Livemail, which backs up each email message into a separate file, Thunderbird seems to place all of its emails into a single mailstore file.

As I schedule a backup daily to NAS storage backing up a single mailstore file daily will take up a lot of space I currently take a full backup every 28 days and keep three full backups and the incremental changes between.

Now for my question - Does Duplicati cope with this situation well? Are there any Thunderbird users who are using Duplicati?

I am also concerned about the fact that Duplicati is still in beta although it has been in development for several years. If there had been a stable version I would probably have changed to it long time ago.

I am in the process of changing computers so it would be an ideal time to change my backup strategy.

Hello and welcome!

I can’t speak to Thunderbird specifically, but I use Outlook and used to use PST file storage for email. This is a single file that stored all my emails. Duplicati uses deduplication, so each backup of this PST (which changed a little bit every day) did not require a huge amount of storage on the back end. I am going to guess that Thunderbird datastore will be similar. You’ll know for sure once you start using Duplicati - you’ll be able to monitor how much the back end size increases after a backup.

Note that with Duplicati every backup job is effectively a “full” backup - you can restore any file from your backup selection from any backup “version.” But they are also “incremental” in the sense that only new files and modified portions of changed files are saved in the back end storage. This is due to its deduplication engine.

So when you’re testing Duplicati, you don’t have to think of the old school “weekly full” and “daily incremental” strategies. Just schedule backups to happen as often as you like and configure how long you want backups to be retained.

The “beta” versions are pretty stable in my experience. A new beta should be released soon, and until that happens I’d recommend using the version.

Thank you - I think I will have to take the plunge and try our Duplicati. As a now retired system architect for many years I like the concept but my programming skills are quite rusty now. I was the leader of a multi-user OS team in the around 1975 1970s. As an aside we supported 70 concurrent text mode users on a Modular one (UK computer) and the memory limit was 256 kilobytes and the largest disk we had was 50 Mbytes!

My background makes me cautious to an extent and I tend to avoid beta software and experimental versions unless I am very close to the development team. If I were not contemplating migrating to Thunderbird I would stick with Cobian which has served me very well for very many years.

I intend to have a test using a W10 virtual machine before finally making up my mind. I have already installed Duplicati but possibly not the version you are recommending.

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You can be on the development team if you like. :wink: Duplicati needs more volunteers than it now has.
That’s basically the reason progress is slower than some may like. It’s not just programming though.

How the backup process works might be of interest. The reason I’d think it will do Thunderbird well is Compacting folders where it sounds like new messages (at least for POP3, not sure about IMAP) get appended to the mailbox, and deletions are flagged but are just a local edit, not a massive file rewrite. Periodically the compact does that massive rewrite, and at that point the backup of changes gets big.

I believe with a Cobian incremental, it’s always whole files. With Duplicati, it’s incremental at 100 KB (default – large backups may like larger) deduplication blocks, so fits Thunderbird between compact.

It’s (I believe) a more complex backup scheme than Cobian has. It has its advantages, but exception handling has a lot more potential failures to worry about, and field-debugging is basically not practical.

https://usage-reporter.duplicati.com/ shows over 3 million backups per month, and forum sees some problems come up. The repair tools (if needed) usually get the job done. It’s very rare to lose backups completely, however sometimes one winds up starting fresh, and old versions of the data may be lost.

Best backup practice is multiple backups, including something remote. Cobian might still serve some.


From - Sun Apr 25 09:58:24 2021
X-Mozilla-Status: 0009

demonstrates what I mean. That value is a hexadecimal display of flags, and by deleting a message in a local mailbox I changed it from 0001 to 0009, basically setting the MSG_FLAG_EXPUNGED flag in-place.

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You can configure Thunderbird to store each email message in a separate file. See Maildir in Thunderbird | Thunderbird Help
Also, unless I forgot that I changed it😅, but my Gmail imap account in Thunderbird uses maildir.

I use duplicati to backup my Thunderbird profile without any problems.

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I followed the installation guide and managed to get a backup working. I then found a file that was “locked” and it generated an error. I now realise that I need to run Duplcati as a service to avoid this issue but I have found the installation instructions confusing. I am still experimenting in a VM environment.

Is there a simple step by step guide to get Duplicati to run as a service but with the backup scheduled to run every day? I am sure it is simple once I have worked out (and documented) how to do it but it would be even better if one already existed.

What checks which files need to be backed up. is the Archive bit used or some other criteria?

Some of my questions are based on my membership of a local computer club where I maintain a support site where tried and tested software is published. I provide technical guidance to our members on useful and reliable software. Backup is coming up on our agenda quite soon.

One question that crops up regularly however is can I initiate a backup job automatically when I insert a specific USB external drive. Some commercial software can do this but I am not aware of any Open Source projects that do. I personally have a NAS that is permanently available.

The club site URL is www.gxcc.org.uk and my related support site is www.soroban.co.uk/gxcc.