In the WAN Utilization section of the Connectivity object on Services > File > Connectivity you can specify both the maximum allocated bandwidth and Minimum roundtrip delay.
If I have an ADSL2 link from the site to the core the speed down to the site is much higher than the speed up. Is there any recommendation on what I should set the bandwidth as? Since the file server is in the core I am guessing we should see more traffic going down than up, so I have been setting it at about half way between the down and up speeds.
My other question is what is the minimum roundtrip delay used for? Does this determine when the WAFS device uses its functionality and when it just passes un-optimised requests straight through to the server?
The connectivity directive settings you are talking about should reflect the maximum BW that CIFS should use on your link. You can try to set that to half way, but keep an eye on CIFS uploads/saves operations. If they are suffering, then you should scale that back to the upload speed.
The BW and Latency parameters are used to attempt to "fill the pipe" with data (i.e. WAAS will attempt to push more data onto the pipe) using a concept called Bandwidth Delay Product.