Disaster tolerance for Oracle databases

With the advent of the global information Age, information data has become the focus of enterprises, that is, in all kinds of natural disasters or man-made damage, how to ensure the safety of production data and key business of uninterrupted operation. Traditional methods of protection offline backup, backup media offsite preservation to some extent can solve the above problems, but in order to be able to provide higher real-time and reliability of business systems, to ensure that the key business 7x24 uninterrupted, to deal with fierce market competition and improve customer satisfaction, enterprises must be in the IT system around the "continuous" (BC) Topics to build, implement business continuity/disaster recovery backup plan, including business continuance, high availability management, disaster tolerance, data replication and restore scenarios, security, and so on, the following is a simple introduction to data replication technology.

Depending on where the data is replicated, you can divide the data into the following four ways:

Based on Storage (storage-based): On behalf of the vendor has EMC SRDF, IBM Pprc/gdps, HP businesscopy, HDS truecopy, etc., the characteristics of the host transparent, less impact on the application system, mature technology, there are more successful cases, But the investment is big, the request to the network connection is also high.

Server-based (host-based): On behalf of the manufacturer is mainly Symantec Veritas Volume Replicator (VVR), is the storage volume replication technology. Need to occupy a certain system resources of the host.

Storage switch (san-based): Run on a dedicated device hooked up on a storage network, on behalf of a vendor with Cisco's Santap,falconstor Ipstor,topio Sansafe,datacore sansymphony, Asynchronous Internet Mirroring (AIM).

Based on database/software applications: On behalf of manufacturers have Oracle dataguard,quest SHAREPLEX,IBM-DB2 remote Q Replication, Sybase replication server (Replication server) and so on, these technologies are to the data logic operations replication , which belongs to logical data replication, while the other 3 replicate the data changes in the data volume, which are physical data replication. The typical logical data replication is realized through database log, the advantage is that the hardware investment is small, the impact on the production system is small, the hardware platform of the main and standby system is not selective; it can be used in the wide area network. However, it has strict requirements for the database system, and the primary and standby systems must use the same database version.

The major vendor scenarios and products described above can be found in the following figure:

This article mainly introduces the data replication VVR based on host and logical volumes.

Veritas's VVR (Veritas Volume Replicator) is a data replication software for effective disaster recovery that allows one or more copies of the application data to be protected continuously. The main advantages are: High performance, unlimited distance, support heterogeneous storage and operating system, continuous protection of data, support synchronous and asynchronous replication.

The VVR system architecture is shown below: