1. A method for enabling high availability and load sharing of highly-replicated applications in computer clusters, the method comprising the steps of: (a) providing at east two computers operationally connected to each other; (b) designating a plurality of identical application groups, wherein each said application group includes one active application and one standby application that: (i) have synchronized state parameters; (ii) have synchronized security policies; and (iii) are configured to run on different computers of said at least two computers, and wherein each said application group includes one backup application, and wherein respective backup applications have non-synchronized state parameters and synchronized security policies with respective application groups; (c) initially allocating said plurality of application groups to said at least two computers such that active applications are distributed according to an allocation policy among said at least two computers; (d) upon detection of at least one event during application operation: activating said respective standby applications to newly-designated respective active applications, while changing said respective backup applications to newly-designated respective standby applications, only for application groups affected by respective events in order to continue said application operation.