|First, you want to setup a separate File Servers do not host the files on your DC or AD server. Then you can setup File Replication Services. |
The best results come from servers with the drive partitions and space setup exactly the same so you don't have to worry about one of the servers running out of space without you knowing about it.
Then you setup you Home and Share directories with the exact same ACLs. Then go in and setup a the DFS Management under Administrative Tools. Go down to replication and create a new group. Follow the wizard. This will setup a replication. Start Loading the files on you Source File Server and they will start to replicate to the backup file server with in 5 minutes or what ever you have the sync set to.
If you do this with a live system MAKE SURE YOU DO A COMPLETE BACKUP WITH ACLS AND ALL PROPERTIES. If you do the replication the wrong way it will delete all of your files in place of the structure on the other server.
Now if you want the system to be completely fault tolerant then you may want to use Name Spaces. I try to steer clear of them because when they mess up they messup big time
With Name Spaces you can use Name Space referencing in your drive mapping script in place of UNC pathing. What this does is use the equivalent of a pointer to the files so that if one of the servers was to go down the users would still see their files through the pointer regardless of which server went down.
WARNING Name Spaces have built in replication and if you use it make sure to remove DFS Replication Groups First or you will get into a replication storm and wipe out both servers. You even get a warning if you try this that says that Unpredictable Results may occur. How do I know this, because I did it, One of the biggest mistakes of my life.
Also, note that I have tried using Name Spaces for a little while and it seems to be buggy to me. Some strange problems came up when using them. I went back to using DFS Replication groups and just switch the server reference in my Login Scripts if I have to bring one of the servers down. Its not seamless but it only takes a few seconds for every one to log out and back in.
I recommend you do some reading on how Name Spaces work and use test servers before you start but when it works, it is a wonderful thing. Especially if you have remote offices that you can replicate to to have off site backups. I run my backup scripts off of the replication server so it does not slow down the active file server and it works well for me.
As with any thing this complex I recommend you get a consultant.