I will answer myself now that I got it working.
1. Install MS SQL 2008 Standard to two servers
2. Install ePO 5.0 to one of those servers (the one that is going to be the master/principal)
3. Backup ePO through the snapshot Dashboard to that database
4. Shutdown ePO
5. Backup ePO database from Principal with logs.
6. Import that backup to Mirror SQL server with no-recovery
7. Setup Database mirroring according to this guide
8. Fire up ePO
9. you are done!
If ePO or the Principal is lost, just start ePO 5.0 install and choose recovery install. Tell Mirror SQL to go in recovery mode and quit mirroring. Tell ePO installer where mirror server is. Change DNS so the new ePO installation matches the old host name of the ePO. Clients didn't know ePO was gone for a while