> uploading large amounts of data to [Backblaze B2] is very slow
All reports we (Backblaze) hear is that if you only use one thread, Backblaze B2 is slightly slower than S3 (like maybe 90% of the performance). If somebody has better numbers I would LOVE to see them!
If clients use multiple threads, this issue goes entirely away. Using 500 threads can provably be 500 times as fast with Backblaze. This is because the Backblaze B2 architecture means there are no "choke points" like Amazon S3 has. Each thread will most likely be talking to a completely different "Backblaze Vault" maybe even in a completely separate Backblaze datacenter. Since they don't share any network switches or load balancers in common, there is no way they will slow down.
But again, I would love any measurements or reproducible tests showing differences so we can chase them down and improve Backblaze B2!