Optimal settings for Backblaze B2 repositories?

[pbowyer]

I'm using other backends no issue, but the Backblaze B2 service is causing me problems! Can anyone share their config that's working for them?

Backstory

I'm backing up a 80GB set of files, mostly small files but with one 9GB file. I configured a new B2 bucket, ran rustic init and then started backing up with rustic backup.

And I kept getting this error over and over:

B2Error { status: 503, code: "service_unavailable", message: "no tomes available" }

This error means that the storage backend at B2 has run out of space; the "fix" as I understand it is to get given another backend to talk to and try and try again until it works.

Finding this thread on the Duplicati forums the first change I made was increasing the number of retries (see: #1091). I couldn't find an exponential backoff setting for rustic, so went for a high number of retries.

[repository.options]
...
+retry = "25"

Now it ran for longer, but still failed with "no tomes available".

Thinking I might have too many transfers going on, and based on this rclone post about problems on a fast connection which didn't happen on a slower connection, I added these two settings to throttle down the transfers:

[repository.options]
application_key_id = "****" # B2 application key ID
application_key = "***" # B2 application key secret. Can be also set >
bucket = "mybucket" # B2 bucket name
bucket_id = "****" # B2 bucket ID
+connections = "10" # Only opendal backends; Default: Not set
+throttle = "10kB,10MB" # limit and burst per second; only opendal backends; Default: Not set

It ran for a while, and then I go this error:

rustic_core experienced an error related to the backend.

Message:
Writing file data/06/06c173d18bf2431af352d3bd46aa3e9ca0e1d4edf39c558717387316fc053c85 failed in the backend. >Please check if the given path is correct.

Some additional details ...

Context:

• type: Pack
• id: 06c173d1

Caused by:
RateLimited (permanent) at => InsufficientCapacity due to burst size being smaller than the request size

So I changed the throttle setting to:

throttle = "10kB,100MB"

That average speed setting was too low, but I ran out of enthusiasm there and stopped. To be continued...