There are a number of configuration knobs available to tune the OpenAFS for Windows client. The most important related to throughput fall into two categories:
How much data can I cache?
How Fast Can I Read and Write?
All of these options are described in Appendix A of the Release Notes. Here are the values I use:
CacheSize = 60GB (64-bit) 1GB (32-bit)
Stats = 120,000 (64-bit) 30,000 (32-bit)
BlockSize = 4
ChunkSize = 21 (2MB)
EnableSMBAsyncStore = 1
SMBAsyncStoreSize = 262144 (but would use 1MB if I didn't use cellular networks as often)
RxMaxMTU = 9000
SecurityLevel = 1 (when I need speed I use "fs setcrypt" to adjust on the fly)
TraceOption = 0 (no logging)