It is possible to specify more than one LDAP server for the user/group directory so that if one fails another takes over:
Set local.ugldaphost to the multiple LDAP machines. Example:
configutil -o local.ugldaphost -v "server1 server2 ..."
Set local.ugldapuselocal to yes. This specifies that the user/group LDAP configuration data will be stored in the local configuration file. Otherwise, it is stored in LDAP. Example:
first server on the list fails, the existing LDAP connections will get recognized as down and new connections will be made. When a new LDAP connection is needed, the LDAP library will try all the LDAP servers in the order they’re listed.