We're playing with the SP 2010 Beta ahead of a planned deployment later this year in an academic environment.
We anticipate that the majority of traffic will be through MySites when everything is provisioned so we're looking at how we can plan our SP topology to scale nicely.
An initial thought is to run the main portal on one server, host "Student" MySites on one server and "Staff" on another.
Is it acutally possible to do this easily or are we going down a bad path?
Specifically - can we have 2 different MySites site collections, each hosted on a dedicated server? If so, can we configure SharePoint to work out from the users's logon account type of user they are and route them to the correct server?
Yes this is possible, and is not considered a bad path to be going down. This is a very typical situation for people who have a geographically dispersed workforce (use a local my site but a centralized main site) or who want to separate out the my sites for performance reasons such as yourself.
The only questionable part to to me is why run the my sites on separate servers at this point? I would think you'd get better bang for your (server) buck by separating the regular site from my sites, but keeping the 2 my sites together so they can share resources (and possibly have some failover capabilities? Depends on how many servers you are talking about.)
Anyway - the proper way to do this is to have multiple farms. In your scenario it would be 3 farms:
You can then setup a trust relationship between the main farm and the 2 my site farms, where the main site would publish its services, and the my site farms would consume them.
Within your main farm you can set up an audience for your staff, and another for your users based on whatever criteria separates them. After that, you setup 2 trusted My Sites locations and give them the appropriate URL and audience.