Failed while executing "Backup"

Hey there,
I am trying to set up a backup job, but it keeps failing (see more below). I am backing up just my PC (1 SSD + 1 HDD) onto an external HDD via USB. Can someone help? I dont understand the error messages. The database chunks / Remote Volume Size is set to 20 GB.

If needed, I can provide a full bugreport I generated today, but it has 300 MB.

Thank you all in advance for help

The error message in full (the latest one):
System.Exception: Unexpected number of remote volumes marked as deleted. Found 0 filesets, but 1 volumes
v Duplicati.Library.Main.Database.LocalDeleteDatabase.d__5.MoveNext()
v System.Linq.Buffer1..ctor(IEnumerable1 source)
v System.Linq.Enumerable.ToArray[TSource](IEnumerable1 source) v Duplicati.Library.Main.Operation.DeleteHandler.DoRun(LocalDeleteDatabase db, IDbTransaction& transaction, Boolean hasVerifiedBackend, Boolean forceCompact, BackendManager sharedManager) v Duplicati.Library.Main.Operation.BackupHandler.CompactIfRequired(BackendManager backend, Int64 lastVolumeSize) v Duplicati.Library.Main.Operation.BackupHandler.<RunAsync>d__20.MoveNext() --- End of stack trace from the previous location from which the exception was raised --- v System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() v CoCoL.ChannelExtensions.WaitForTaskOrThrow(Task task) v Duplicati.Library.Main.Controller.<>c__DisplayClass14_0.<Backup>b__0(BackupResults result) v Duplicati.Library.Main.Controller.RunAction[T](T result, String[]& paths, IFilter& filter, Action1 method)
v Duplicati.Library.Main.Controller.Backup(String inputsources, IFilter filter)
v Duplicati.Server.Runner.Run(IRunnerData data, Boolean fromQueue)

System info (generated in bugreport):
Duplicati: Duplicati.GUI.TrayIcon, Version=, Culture=neutral, PublicKeyToken=null (Duplicati.Library.Main, Version=, Culture=neutral, PublicKeyToken=null)
Autoupdate urls:;
Update folder: C:\ProgramData\Duplicati\updates
Base install folder: C:\Program Files\Duplicati 2
Version name: “” (
Current Version folder C:\Program Files\Duplicati 2
OS: Microsoft Windows NT 10.0.19045.0
64bit: True (True)
Machinename: [redacted]
Processors: 12
.Net Version: 4.0.30319.42000
Mono: False (0.0) ()
Locale: [redacted]
Date/time strings: dddd d. MMMM yyyy - H:mm:ss
Tempdir: C:\Users\user\AppData\Local\Temp
SQLite: 3.28.0 - System.Data.SQLite.SQLiteConnection
SQLite assembly: C:\Program Files\Duplicati 2\SQLite\win64\System.Data.SQLite.dll

these values are not wise. Create a new backup with default values and try to backup a limited amount of data. If it does not work, post again the full error messages (or at least the first one, not the last)

If it works, delete your current backup and recreate it with default values. You can raise the block size to 400K if your total backup size is over 1 TB.

Ok thank you, will try and report back

tried as you told me - selected less stuff to be backed up. It works now, but the back up doesnt contain the whole system now, just the most important parts. Maybe because the target drive is pretty close in terms of size to the source files marked for backup it didnt work before.

Thank you for your help.

And btw the default value of the block size is 50MB for me, so I didnt understand what you meant when you wrote “You can raise the block size to 400K if your total backup size is over 1 TB”, but now the backup works nonetheless.

The default value for ‘blocksize’ is 100 KB.
The default value for ’ dblock-size’ is 50 MB.

If you refer to below, click the link in your job Options screen.


and Remote volume size is sort of a synonym for dblock-size. Historical reason for that is unclear.
Possibly a more user-friendly presentation was desired, however IIRC it’s also split in the config file…

Regardless, we might follow this presentation lead to get into blocksize, if nothing better can be found.

I would have said 1 MB for 1 TB, following rough rule that SQL slowdown occurs past 1 million blocks.


Choosing sizes in Duplicati is the “See this page” in the GUI, and looks like it got more comprehensive.
How the backup process works if you’ve read the above page, then really want the deeper information.