Upload speed drop with Backblaze B2

[tms]

Hello,

I recently started using Duplicati and initially tested it with AWS before switching to Backblaze B2. I’m running the latest stable version with default settings, including a volume size of 50 MB.

At first, everything worked smoothly: I achieved an upload speed of around 3 MB/s, which aligns with my 30 Mbit/s connection. However, as the backup progressed, the speed gradually dropped to just 800 KB/s, even though there are still 1.3 TB left to upload.

To rule out a connection issue, I tested a manual upload via Backblaze’s web interface and still achieved 2.3 MB/s, which would be acceptable for me.

I’ve read in older forum posts that compression could be the cause of slower speeds. However, my CPU usage remains low, so I’m not sure if that’s the issue in my case. Do you have any suggestions on how to restore my upload speed?

Best regards,
Thomas

[ts678]

@tms

At first, everything worked smoothly: I achieved an upload speed of around 3 MB/s, which aligns with my 30 Mbit/s connection. However, as the backup progressed, the speed gradually dropped to just 800 KB/s, even though there are still 1.3 TB left to upload.

Is this all one backup? How “at first” is it, e.g. is this the initial backup, or an update to existing?

Updates only upload changes, sometimes they take awhile to gather, and speed is an average.

When there is nothing needing upload, average speed sags, but it picks up again on an upload.

@tms

I tested a manual upload via Backblaze’s web interface and still achieved 2.3 MB/s, which would be acceptable for me.

You can find a somewhat equivalent (not fully because by default 4 uploads can run at once):

log-file=<path> and log-file-log-level=information will show bytes and times. Divide.

or

log-file=<path> and log-file-log-filter=+*UploadSpeed shows a pre-calculated speed.

You can also get UploadSpeed in a profiling level log, but there’s lots of additional info in them.

Example of an upload:

2025-02-16 09:12:43 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-b65e0789fb07642b19599a2322369f4f8.dblock.zip.aes (49.99 MiB)
...
2025-02-16 09:12:57 -05 - [Profiling-Duplicati.Library.Main.Operation.Backup.BackendUploader-UploadSpeed]: Uploaded 49.99 MiB in 00:00:13.7577721, 3.63 MiB/s
...
2025-02-16 09:12:57 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Completed: duplicati-b65e0789fb07642b19599a2322369f4f8.dblock.zip.aes (49.99 MiB)

Although it’s not human-friendly, you can watch uploading status in About → System info.
lastPgEvent has stats like the below, and the calculated speed there should match status:
“BackendFileSize”:20820762,“BackendFileProgress”:6082560,“BackendSpeed”:2019094,

When Progress catches up with size, there’s nothing to do, so speed sags until an upload.

If on the other hand, this is an initial backup, then there are other factors to worry about…