[imp] High Availability / Load Balancing

[Lee]

Hey All,
We're looking into adding a second imp front end server to provide load 
balancing and redundancy to webmail. Forgetting for a minute how to 
implement the actual service redundancy/load balancing (i.e. via 
hardware, dns roundrobin etc...), I wanted to get a feel for how others 
handled the horde/imp/turba specific issues.

Since we currently store all prefs in ldap, I think i have boiled the 
problems that need to be solved down to:

1) Sessions - They're currently stored in files. Could a client be 
reading or composing an email then try to load a page, end up with the 
second horde/imp server (that doesnt have an active session) and be 
logged out?

2) Attachments - Could a user upload an attachment, then send the mail 
(using the other server that doesn't have the attachment) and get an 
error?

Has anyone dealt with redundancy / high availability and found 
solutions to the above problems? Are there any other problems that I'm 
not thinking about?

Thanks,
Lee