The Key buffer is very tunable; I would not recomend it based on installed ram size at all in fact you want this value as small as you can without impacting performance, especially on Windows servers, it needs baselining, for instance I get no real benefit raising mine above 128MB where the key read ratio today is 0.000246443
Donate to UBBDev today to help aid in Operational, Server and Script Maintenance, and Development costs.
Please also see our parent organization VNC Web Services if you're in the need of a new UBB.threads Install or Upgrade, Site/Server Migrations, or Security and Coding Services.