Compacting because there are 21 small volumes and the maximum is 20

fatal error.
What its mean ?

A “small volume” is a dblock (archive file) that is smaller than a specific size.

This is normal and can happen due to things like:

  • the least set of items in backup not fully filling na dblock
  • very few items needing to be backed up in single job run
  • old versions of files being cleaned out of the existing backups
  • you’ve increased the “small size” setting (making any existing dblock files be considered small)

The compacting and deleting of small volumes is triggered when more than a certain number (in your case, 20) of them have been created.

Again, this is normal and Duplicati is simply grouping multiple small dblock files into fewer new ones then deleting the no longer needed small ones.

This maintenance helps keeps the number of detonation files low over time which helps in keeping connections to the destination from becoming slow.

if its normal, why it triggered as fatal error with red tray icon ?
how to disable this notification ?

All 5 items in your screen shot are listed as Message - they should not cause a red tray icon. My guess is something else caused a fatal error and the red tray icon.

Is your list from the job log or the main menu “Show log”?

that was red tray icon on subj message.
Sry no log, because I already recreated task

I found only this error in common log

SharpCompress.Compressors.LZMA.DataErrorException: Data Error
   at SharpCompress.Compressors.LZMA.LzmaStream.Read(Byte[] buffer, Int32 offset, Int32 count)
   at Duplicati.Library.Utility.Utility.ForceStreamRead(Stream stream, Byte[] buf, Int32 count)
   at Duplicati.Library.Main.Volumes.BlockVolumeReader.ReadBlock(String hash, Byte[] blockbuffer)
   at Duplicati.Library.Main.Operation.CompactHandler.DoCompact(LocalDeleteDatabase db, Boolean hasVerifiedBackend, IDbTransaction& transaction)
   at Duplicati.Library.Main.Operation.DeleteHandler.DoRun(LocalDeleteDatabase db, IDbTransaction& transaction, Boolean hasVerifiedBacked, Boolean forceCompact)
   at Duplicati.Library.Main.Operation.BackupHandler.CompactIfRequired(BackendManager backend, Int64 lastVolumeSize)
   at Duplicati.Library.Main.Operation.BackupHandler.Run(String[] sources, IFilter filter)
   at Duplicati.Library.Main.Controller.<>c__DisplayClass16_0.<Backup>b__0(BackupResults result)
   at Duplicati.Library.Main.Controller.RunAction[T](T result, String[]& paths, IFilter& filter, Action`1 method)
   at Duplicati.Library.Main.Controller.Backup(String[] inputsources, IFilter filter)
   at Duplicati.Server.Runner.Run(IRunnerData data, Boolean fromQueue)

Yes, this is the problem. Duplicati is attempting to read the zip file and it contains broken data.

Is the data encrypted? Is it possible for you to share this file (unencrypted)?

no files exist, already recreated DB.
DB currently in Google drive

Not sure what this means? If there are no files you cannot build a database?