> In practice, the global mutexes restricted the fileserver process to 1.7 cores regardless of how many cores were present in the system.
So in theory the bandwidth could scale with single CPU and/or point to point bandwidth but cannot scale horizontally at all. Except on the new implementations.
Correct, and the point-to-point bandwidth is limited by the maximum RX window size because of the bandwidth delay product. As round-trip latency increases, at some point the window size becomes insufficient to keep the pipe full, at which point data transfers stall.
One site which recently lifted and shifted their AFS cell to a cloud made the following observations:
We observed the following performance while copying a 1g file from local disk into AFS.
AuriStor Client (2021.05-65) -> OpenAFS server (1.6.24): 3m.11s
AuriStor Client (2021.05-65) -> AuriStor Server (2021.05-65): 1m
AuriStor Client (2025.00.11) -> AuriStor Server (2025.00.11): 30s
All of the above tests were performed from clients located on campus to fileservers located in in the cloud.
There are many RX implementation differences between the three versions. It is important to note that the window size grows from 32 -> 128 -> 512.
> In practice, the global mutexes restricted the fileserver process to 1.7 cores regardless of how many cores were present in the system.
So in theory the bandwidth could scale with single CPU and/or point to point bandwidth but cannot scale horizontally at all. Except on the new implementations.