Hello!
I start using duplicati on MS Server 2016 (backup custom folders from local to sftp share, aes256).
Welcome to the forum @ilyai
I don’t use Windows Server 2016 (anybody out there using it who has specific additional comment?), but Duplicati probably just sees at as Windows. You might need to make sure .NET Framework is up to date.
There’s never a guarantee that you didn’t back something up the wrong way if you have more than simple closed files. If you have files that are in use by some application, data might not be on drive yet to back up.
Databases are especially likely to give specific procedures, but even desktop applications can have them.
Volume Shadow Copy Service can help with this (by working with VSS-aware applications), if you set up snapshot-policy in Duplicati (which requires putting Administrator privilege in effect, which can be difficult).
There’s never a guarantee that a recovery will work, and whether or not you tune is pretty much up to you. None of this is Windows Server 2016 specific though. For best reliability, you should use several backups.
For large backups, one good tuning for performance is to increase blocksize. This helps database actions. Choosing sizes in Duplicati talks about some other possible tunings, but lots of people likely don’t bother…
I run Duplicati on Windows Server 2019. You’re right, from Duplicati’s point of view it’s just a Windows PC.
I found that duplicati do not install service, so backup complete only after I enter the account. I think I should install Duplicati.WindowsService.
Yes. That’s currently a manual step with Duplicati.WindowsService.exe and a Microsoft pitfall where the SYSTEM profile that Duplicati is in by default gets moved into Windows.old during their version upgrade.
Installing Duplicati on Windows shows a new service install.
Duplicati Tutorial 02 Install Duplicati as a Service is a video.
Migrating from User to Service install on Windows is a forum topic that gets into configuration migrations.