How to implement this kind of architecture?

[<sparklezou@hotmail.com>]

Dear Kurt and all,

  I would like to implement the following kind of DIT. Please give me some 
comments.

       Front End
      /         \
     /           \
Backe End 1    Back End 2

1.The Front End is the interface to the client. And it is only forword the 
data request to the Back End. And also support the client authorization.

2.The Back End stors the data.

My solution:
  1. on Front End, configure as "meta" backend to work as an proxy to 
forword the data request to the Back End. And also configure as "bdb" to 
store the client authorization infomation.

  2. On the Back End, configure as "bdb" backend to store the data. And in 
the slapd.conf file also set the refer to the Front End.

  If I would like to add 3 DS in the Front End and Back Ends to implement 
HA. How to implement it? Could I use replicate?

          Front End(3DS)
         /         \
        /           \
Backe End 1(3DS)    Back End 2(3DS)


  Thank you very much!

  Waiting for you kind replay!

                                                         Best Regards,
                                                         Zou Yu