The third pillar of mission-critical systems is scalability; reliability and availability are the other two, creating the acronym RAS.
Applications often require additional capacity during critical times. Scalability is an inherent and important attribute of mission-critical systems, since both the servers and the database must be scalable. Active/active systems can provide scalability to servers as well as the database. However, adding physical servers and disk systems to achieve greater capacity is typically not feasible, especially for temporary additional capacity needs. Scalability can be achieved via the use of active/active systems and Pathway domains that span multiple HPE NonStop systems. It can also be achieved by bursting applications to RAIC servers (inexpensive commodity hardware) that are deployed in one or more clouds, where it can be reused between applications, providing an economic cloud platform for scalability on-demand.
For NonStop users, maximizing the RAS for mission-critical systems can now be accomplished by leveraging the new Virtualized NonStop technology.
Article:
Achieving Scalability for Mission-Critical Systems in the Cloud