Backend quota has been exceeded after apparently successful backup


Destination: macOS 10.13.6
Target: Enterprise object storage mounted with LucidLink (FUSE)
Duplicati: (I tested first with
MonoVersion :

I am new to Duplicati and trying to make everything work. When I complete a backup, I keep getting the following error message:

[Error-Duplicati.Library.Main.Operation.FilelistProcessor-BackendQuotaExceeded]: Backend quota has been exceeded: Using XXX.XX GB of 0 bytes (0 bytes available)

It seems as the backup completes successfully and I’m able to restore some files while testing. According to LucidLink, there are vast amounts of storage available at the target, and the local storage is fine as well. So I have no clue where to go from here.

Any help is appreciated, thanks.

Support for FUSE mount points

Hello @keen and welcome to the forum!

I have neither LucidLink nor a Mac, so can offer only limited help, but I found recent work on space reporting:

Release notes for build #1488, release September 18, 2018

Release notes for build #1520, release October 11, 2018

That sounds like two different measurement mechanisms. Can your local storage measurer also measure the available storage at the LucidLink mount? This mentions some ways including an easy one using Quick Look. From the command line, perhaps you can run a df command, which perhaps runs statfs (see build #1488).

Duplicati.CommandLine.BackendTester.exe gives space information at the end of its test, based on DriveInfo.

As a side note, LucidLink’s use of a write cache worries me because the actual upload is delayed (till when?).



I am still experiencing this issue. I opened a case with LucidLink, who looked into the problem, looking through logfiles and ended up sending me back to Duplicati after looking through the source code as well, claiming the issue isn’t related to the storage itself.

I am currently running the latest version:

The issue seems to be caused by how Duplicati determines the QuotaInfo for the backend path, when the backend is a local FileSystem path. It go to the root of the path and then get the quota for that. Duplicati’s default backend (Duplicati/Library/Backend/File/FileBackend.cs) write logic implements very rudimentary quota system. I was recommend logging an issue here, explaining that sending a Duplicati backup to a FUSE mount point (which is what Lucid uses to mount) does not work.


The problem still present with