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This article introduces the relevant knowledge of "what are the concepts related to database backup and disaster recovery". In the operation of actual cases, many people will encounter such a dilemma. Next, let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Physical backup: the backup process of copying the operating system files that actually make up the database from one place to another, usually from disk to tape. Physical backup is divided into cold backup and hot backup.

Logical backup: refers to the use of software technology to export data from the database and write to an output file, which is generally different from the file format of the original database and is only an image of the data content in the original database. Therefore, logical backup files can only be used to logically restore the database, that is, data import, but can not be physically restored according to the original storage characteristics of the database. Logical backups are generally used for incremental backups, that is, backing up data that has changed since the last backup.

Cold backup: when the database can be temporarily closed, we need to transfer its data-related files at this stable time to a secure area, and when the database is destroyed, then copy the backed-up database-related files from the security area back to the original location, so that a quick and secure data transfer is completed. Because it is in a closed state where the database does not provide services, it is called a cold backup.

Hot backup: when we need to make a high-precision backup, and it is impossible for our database to stop (a little traffic), in this case, we need a backup in archived mode.

Disaster recovery: refers to the establishment of two or more IT systems with the same function in distant places, which can carry out health monitoring and function switching between each other. When one system stops working due to accident (such as fire, earthquake, etc.), the whole application system can be switched to another place, so that the system function can continue to work normally.

Data-level disaster recovery: remote backup of data through the establishment of remote disaster recovery centers to ensure that the original data will not be lost or destroyed after a disaster, but at the level of data-level disaster recovery, the application will be interrupted in the event of a disaster. In the data-level disaster recovery mode, the established remote disaster recovery center can simply be understood as a remote data backup center. The recovery time of data-level disaster recovery is relatively long, but compared with other disaster recovery levels, its cost is relatively low, and the construction and implementation is relatively simple.

Application-level disaster recovery: on the basis of data-level disaster recovery, a set of the same application system is also built at the backup site, through synchronous or asynchronous replication technology, which can ensure that the key applications resume operation within the allowable time range, minimize the loss caused by the disaster, so that users basically do not feel the occurrence of the disaster, so that the services provided by the system are complete, reliable and secure. The data transmission between the application-level disaster recovery production center and the remote disaster recovery center adopts a heterogeneous WAN transmission mode; at the same time, the application-level disaster recovery system needs to be realized through more software. can make a variety of applications can be quickly switched in the event of a disaster to ensure business continuity.

Business-level disaster recovery: disaster recovery for the whole service, in addition to the necessary IT-related technologies, but also requires all the infrastructure. Most of its contents are non-IT systems (such as telephone, office, etc.). When a catastrophe occurs, the original office will be destroyed, in addition to the recovery of data and applications, but also need a backup workplace to be able to do business normally.

CDP (continual data protection): continuous data protection.

MTTF (mean time to failure, mean time before failure): defined as the "expected value" of random variables, error time, etc. However, MTTF is often misunderstood as "the shortest life cycle that can be guaranteed". The length of MTTF is usually related to the product in its life cycle, excluding aging failure.

MTTR (mean time to restoration, mean time before recovery): the purpose is to clearly define the concept of time in the term, MTTR is the expected value of the recovery time of a random variable. It includes the time necessary to confirm that the failure occurred, as well as the time required for maintenance. The MTTR must also include the time to get the parts, the response time of the maintenance team, the time to record all tasks, and the time to put the equipment back into use.

MTBF (Mean time between failures, mean time between failures): the average time required for failure or maintenance, including failure time and time spent testing and maintaining equipment. For a simple maintainable component, MTBF = MTTF + MTTR. Because MTTR is usually much smaller than MTTF, MTBF is approximately equal to MTTF and is usually replaced by MTTF. MTBF is used for maintainable and unmaintainable systems.

RTO (Recovery Time Objective, recovery time goal): is the length of time that an enterprise can allow a service outage. For example, if you need to recover within half a day after a disaster, the RTO value is 12 hours.

RPO (Recovery Point Objective, recovery point target): refers to the interval point corresponding to the recovered data when the service is restored.

Snapshot (Snapshot): a fully available copy of a specified data set that includes an image of the corresponding data at a point in time (the point in time at which the copy begins). A snapshot can be either a copy of the data it represents or a copy of the data.

Mirroring: a type of redundancy in which there is an identical copy of data on one disk on another.

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