Backup: selective scheduled backup of .dtsparse while working on opened ones

I still ask for the best way to make backups. Premise: I represent the case in which I use Arq for a remote backup on cloud service. First question: is it correct to select individual.dtsparse databases for scheduled backup every two hours while they have been opened working on them?

No.

DEVONthink (DT) databases can have three different file endings:

  • .dtBase2 (unencrypted database, whether open or closed)
  • .dtSparse (encrypted database, when closed)
  • .sparseimage (encrypted database, when open)

The easiest way to reliably back up your databases is to backup the whole location where they are stored (so /Databases for example). That way each database will be backed up regardless of whether or not it is currently open in DT. If, in Arq, you select the option Keep deleted files in subsequent backup records, then it is easy to find the latest copy of the database.

If for some reason you want to specify individual files for backup, then - for encrypted databases - you should include both database.dtSparse and database.sparseimage in your backup. That way, Arq will back up the database regardless of whether it is currently open or closed in DT. As you are aware, AFAIK, technically speaking the database is transferred as an encrypted sparseimage regardless of whether it is open or closed in DT.

The disadvantage of the single file approach is that Arq will report an error (it can’t backup database.dtSparse, because that file will be missing when the database is open in DT; and vice versa, it can’t back up database.sparseimage, because that file will be missing when the database is closed in DT). For me, those error messages are a helpful reminder: I have two backup series configured in Arq - one for open and one for closed databases. That way I can easily check to see when the last backup of closed databases was. My databases are mostly open - so I need my backup software to back up open databases; but best practice suggests only a backup of a closed database is fully representative of the database, so I want at least occasional backups of closed databases too.

Additional unsolicited info: I don’t back up all my databases to Arq (for data protection and associated legal reasons). I make a hard copy of closed databases to WORM once a month. My databases are also backed up to external media using both TimeMachine and CCC.

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In addition to @blanc’s terrific response, take a look at page 19 of the outstanding DEVONthink Handbook “A Word about Backups”. In particular, see how to create zip file backups that you can have your Arq program backup, in addition to the whole location.

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Thank you, you have been very clear. But I wanted to ask you what you mean when you say that “I don’t back up all my databases to Arq (for data protection and associated legal reasons)”. I make encrypted Arq backup of encrypted database. Is it not enough?

link me where i can get this handbook, please

I would think that is enough, yes. Where I live, laws (or quasi laws) govern that some data may not be uploaded to servers outside the country, and then only if the servers to which the data is uploaded are certified to certain standards.

If you are not under such constraints, uploading encrypted databases to an encrypted store should be pretty safe (not 100 % because errors In implication, brute force, quantum computing or whatever).

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but with the zero-knowledge encryption you might not have problem concerning constraints on uploads

In addition to the link provided by @Blanc the same content is in DEVONthink Menu: Help. You can search for the backup section I mentioned.

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