Just would like to know whether SUSE Manager supports cluster (Active - Standby / Active - Active).
from what I know there should be a paper in the works that describes a HA setup for SUSE Manager. But this will for sure be based on SUSE Manager 3.2. But you should update to this version anyways, as 3.1 support ends on 30th of june this year.
I'll get back when I know more about the HA paper. But in general we advice to use SUSE Consulting or an experienced Consulting Partner of SUSE for an HA implementation.