Oracle RAC HA

Ha, which only monitors and manages the database at the operating system level, is generally used only for single-instance databases. The advantages are convenient management, convenient application development (developer convenience), and less project input. The disadvantage is that it has all the disadvantages of single-instance database: Poor fault tolerance, poor endurance, small user capacity and so on.
RAC, the database itself provides a single database multi-instance application method, the advantage is: 1, the use of flexible, can be used as a single machine can also be used in multiple machines. 2, provide a large number of users access to a solution, that is, multi-machine parallel operation of the database running in the memory, CPU and other system resources. 3, the fault-tolerant ability is higher than the single machine, especially in the fault tolerance of host class problem. (This is not the problem with magnetic arrays). Disadvantage: 1, the development requirements are high, need to configure the balance mode alone to reflect its advantages. 2, the investment is high, both hardware and software need to invest alone.
(But in fact, if the requirement is not high in the software investment, the two schemes are similar, are the basic configuration of two machines plus a magnetic array


Rose ha

Oracle RAC HA