replication of domain login service

[Dirk Maaß]

Hi all!
Is there any way to replicate the samba domain login service to other
servers?

I have set up an ldap directory (iplanet directory servers with a
replication structure) that is used as name service for linux and
solaris clients and I want to install a samba 2.2 server (Solaris 8) as
PDC for the Windows 2000/NT machines.
Samba should be used because I hope the user mapping and account
synchronization between the NT and Unix worlds can be implemented
easily.
To improve availability a second samba domain server needs to be
implemented (may be Solaris, too) so that NT users can still log in to
their
machines when the samba-PDC is temporarily not available (broken network
connection or whatever).
 
As I understand Microsoft networks there can be just one PDC in domain,
replication of the user database is done through backup domain
controllers. As I have read, samba 2.2. can not be used in a replication
szenario. (right?)
 
So I wonder if there is a possibility (workaround or another helpful
idea) to achieve that the NT users can log in when the PDC is not
online. 

Any help would be appreciated.
 
Dirk Maass