You can observe all topics with this tag: Topics tagged nfs
For short: NFS is not compatible with SQLite databases and not all implementation of NFS are compatible with DB, which is used for blobs. As a summary - the NFS is not supported and not recommended.
As you can see on your own example, it has issues.
You should measure the mounted disk subsystem, not the network throughput. You will notice a high latency when you have a deal with small chunks of data