Very poor file sharing performance over VPN site-to-site

Hello,

we are using a server client software which is installed on a Azure VM. To access the database the clients need to connect a NTFS fileshare from the cloud server. Unfortuately the read/write performance for the network share is very poor. We are facing a throughput of around 300KB/s. We are using a route-based Site-to-Site VPN to connect to Azure.

Does anybody know how we can speed up the connection?

Thank you very much and kind regards

Constantin