Oracle Dual-Machine hot standby, Oracle Dataguard and Oracle RAC Differences and linkages

Data Guard is a remote replication technology for Oracle, it has physical and logical points, but in general, it needs a separate system in a remote location, two sets of hardware configurations can be different systems, but the software structure of the two systems are consistent, including the software version, directory storage structure, and data synchronization (in fact, is not real-time synchronization), the two sets of systems as long as the network is a pass, is a disaster-tolerant solution. For RAC, it is a locally high-availability cluster, where each node is used to share unused or identical applications to solve problems such as inefficient operation and single-node failure, which is made up of several identical or different servers, plus a SAN (shared storage area).

Data guard consists of two more than two separate databases, each of which has its own storage, and Oracle is responsible for switching between them and synchronizing the data. Dual-machine hot standby is made up of two computers and a shared storage device, which can be switched through third-party software (HA rose, etc.) without the need for data synchronization

It is recommended to apply Rac+dataguard, RAC guarantees availability, Dataguard on the RAC group stand-alone disk and on another host, ensuring reliability.

Double machine is what people call the dual-machine hot standby, the database on the shared device, the same time can only have one host to take over, the other to be used, this way can only protect the instance, can not protect the db, and the standby machine is idle for a long time, the resources is a great waste!

If the original is a dual machine, it is recommended to convert to RAC to plan the application, DML operations run from one node, query operations run from another node, usually do not need too much tuning to take advantage of another idle machine

The RAC server uses a single set of storage, while providing services, without the primary and standby points. One of the other services can be continued. Two-machine hot standby, a shared set of storage, a service to provide a backup, the host outage switch to the backup server to provide services. Data Guard is completely two sets of systems, the storage is separate, with the log synchronization.

RAC: Instance layer redundancy DG: Database layer Redundancy hot standby: just data redundancy

Personal Understanding: RAC: Instance redundancy, but also can do the database loadbalance. DG: Multiple data, so you can do data redundancy, but only the primary node provides services. Hot-Standby: The biggest difference from RAC may be that there are multiple instances of RAC, one database. And the hot standby is just an instance, a database. So you can't do concurrency and loadbalance.

Oracle RAC is just an application for Oracle, and Rose,legato can do other

HA:is the first letter combination of high availability, translated, can be called highly available, or high availability, high availability (environment). I think it should be said that HA is an idea rather than a specific or a series of technologies, just like a grid. Once the system has been worked out, the performance of the evaluation system is highly available. The broad range of high availability involves all aspects of the system, which simply means that the system does not interrupt operation, but is highly available. Including high availability of software, high availability of hardware, high availability of the network and so on. The implementation of the program includes the operating system cluster, the database cluster, hardware redundancy, network redundancy and so on. Do HA software, has IBM's HACMP (many commonly used AIX people, often said Ha refers to hacmp, disorderly AH), Sun Sun Cluster, HP Mc/sg and so on.
Before 2000, we talk about Ha, most of the time is operating system-level dual-machine hot standby, mainstream products at that time IBM hacmp4.1,hp mc/sg what version forgot, Sun's system many people do not use VCs, with a call dataware things. Ha is still the same in many people's eyes now. Today, Ha includes more things, not to mention other aspects of the database alone, Oracle, and HA-related products have: Advanced Replication (Advancerepication), Ops/rac (Real application Cluster), Data Guard, Oracle Streaming (Oracle Streams), partitioning (Oracle Partition), a number of products. According to this, RAC is only a specific product under the HA concept! So far, only the RAC and partition is Oracle to charge licence, the other, as long as the experienced third-party implementers to pay a certain amount of planning/design and deployment costs can be, of course, you can follow the document according to the gourd, but it is difficult to make the environment to achieve high availability. In fact, most people say that ha, or the narrow sense of ha, is the OS-level dual-machine hot standby.
RAC:is the short name of real application cluster, which is the technology that runs a database on multiple hosts, which is a DB multiple instance. It has the advantage of being able to build a well-performing cluster of multiple poorly performing machines and load balancing, so that when one node fails, the service on it automatically goes to another node to execute, and the user doesn't even feel anything.What is the difference between a two-machine hot standby (HA) and a RAC?
1, for the hardware, basically the same, shared storage, fiber optic cable (also with SCSI cable), a number of small machines (can be multi-node hot standby, can also do a long node RAC), fiber switch (if the use of fiber-optic card); but do RAC, between the hosts, It is best to use a high-bandwidth network switch (although it is not possible), so the hardware cost is small. 2, the software, the difference is not small. If the dual-machine hot standby, must buy the operating system level of dual-Computer Management software, if it is RAC, it is still recommended to buy dual-Computer Management software (although 10g crs+asm can get rid of the dual-computer software, but ASM is too difficult to wait), of course, also have to buy RAC license. 3, daily maintenance. RAC requires a higher level of technology and should be more diligent. The key is to buy Oracle services, or if you encounter some problems (bugs), you are more than a single machine is not high availability. 4. Advantages and disadvantages. This, look at the official description of RAC. It's really good if you can use it well. At present, the use of our more than 40 customers, RAC does greatly reduce their downtime, on the other hand, can be said to improve productivity.
Dataguard: generally for the purpose of disaster tolerance. is the primary database of the standby library (standby library) through the automatic transfer and acceptance of Archivelog, and in the Dataguard library automatically apply these logs, so as to achieve the purpose of synchronization with the primary database, it is possible that the Dataguard library is established offsite, When the main library is located in the area of a fatal disaster (fire, earthquake, etc.), the main library can not be repaired, when it is possible to switch Dataguard mode for the main library, to provide services externally, and its data is basically the latest. At present, we may have expanded the use of Dataguard library for other purposes, such as backup, run reports and so on.

"from:http://blog.csdn.net/dream19881003/article/details/6655678"

Oracle Dual-Machine hot standby, Oracle Dataguard and Oracle RAC Differences and linkages (RPM)