After many hours of running COPY from my Win 7 backup computer to Backblaze B2 suddenly I received the following error and the copy process stopped completely:
Chunk ... (44xx/82676) copied to the destination
...
Chunk ... (4411/82676) copied to the destination
URL request 'https://pod-000-1052-13.backblaze.com/b2api/v1/b2_upload_file/26856cb06f097f6b644b0510/c000_v0001052_t0037' returned status code 500
URL request 'https://pod-000-1054-18.backblaze.com/b2api/v1/b2_upload_file/26856cb06f097f6b644b0510/c000_v0001054_t0047' returned status code 500
Failed to upload the chunk e076772755c1bc521914ed01d7833e156a4bdd2eb84f68f767ac5ae4638a2655: Maximum backoff reached
After restart of COPY it runs again for hours now.