Shulou(Shulou.com)06/01 Report--

There is a relationship between disaster recovery and backup.

1. The purposes of disaster recovery and backup are different.

The purpose of disaster recovery system is to ensure the "linearity" of system data and services, that is, when the system fails, it can still provide data and services to the network system normally, so that the system will not stop. The purpose of backup technology is not the same, backup is "the process of transferring online data into offline data", its purpose is to deal with logic errors in system data and historical data preservation. Therefore, in a variety of fault-tolerant technologies are very rich today, backup system is still irreplaceable.

two。 Backup is the cornerstone

Backup refers to the process of copying the whole system or part of the data set from the hard disk or array of the application host to other storage media in order to prevent data loss caused by system error or system failure. Backup is the last line of defense for high availability of data, and its purpose is to recover data when the system data crashes.

3. Disaster recovery is indispensable.

So after building a backup system, does it mean that there is no need for a disaster recovery system? It also depends on the expectation of the business unit on the RTO (time indicator required for recovery) / RPO (latest status that can be restored). If the database of 1TB is allowed to have RTO=8 hours and RPO= for 1 day, then the backup system can meet the requirements. At the same time, the purpose of backup is to deal with logic errors in system data and historical data preservation. It can only meet the purpose of data recovery in the event of data loss and data destruction, but can not provide real-time business takeover function. Therefore, disaster recovery system is also essential for some key services. People often talk about disaster recovery when the production system can not work properly, its business can be replaced by the disaster recovery system and continue to work normally. Can provide good RTO and RPO indicators. At the same time, the remote disaster recovery system has the ability to cope with all kinds of disasters, especially regional and destructive disasters, has relatively perfect data protection and disaster recovery functions, ensures the integrity of temporary data and business continuity in disaster reduction, and resumes the normal operation of the business system in the shortest possible time to minimize losses.

4. Disaster recovery cannot replace backup

The disaster recovery system will completely copy any changes in the production system to the disaster recovery side, including the work that you do not want it to copy, such as accidentally deleting the user information table in the billing system. At the same time, the user information table on the disaster recovery side will also be deleted completely. If it is synchronous, the disaster tolerant end will be deleted at the same time; if it is asynchronous disaster recovery, the disaster tolerant side will be deleted within the interval of asynchronous data replication. At this point, you need to take the latest backup from the backup system to recover the information that has been mistakenly deleted. Therefore, the construction of disaster recovery system can not replace the construction of backup system.

5. Interpretation of "RTO\ RPO"

RPO is the length of time for problems such as data loss in your system to indicate the situation of data loss at intervals in the system.

How much time does RTO take for your system to reply, which is also the length of time it takes to restart in your system?

So the values are all time.

RTO is an indicator of the timeliness of business recovery, indicating the time it takes for business to return to normal from interruption. The smaller the RTO value is, the stronger the data recovery capability of the disaster recovery system is. The RTO of various disaster recovery solutions is quite different. Synchronous data replication based on optical channel technology, combined with remote standby business system and high availability management across business centers and backup centers, this disaster recovery solution has the smallest RTO. Disaster recovery system needs to invest a lot of money in order to obtain the minimum RTO.

RPO is an indicator of restoring data integrity. In synchronous data replication mode, RPO is equal to the time of data transmission delay; in asynchronous data replication mode, RPO is basically the queuing time of asynchronous data transmission. In practical application, considering the data transmission factors, the consistency (SCN) of the business database and the disaster recovery backup database is different. RPO represents the time difference between the SCN of the business database and the disaster recovery backup database. After a disaster, start the disaster recovery system to complete data recovery, and RPO is the amount of data loss of the new recovery business system. The RTO and RPO of different disaster recovery schemes are different.

RTO (Recovery Time Objective, recovery time objective) is the length of time an enterprise can allow for service outages.

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 time interval between the recovered data when the service is restored. If the enterprise now makes a backup at 00:00 every morning, when the service is restored, what will be stored in the system will only be the data at 00:00 before the recent disaster.

According to the above two simple principles, enterprises can not only make the existing data system, but also choose the most suitable disaster preparedness plan according to the established RTO and RPO requirements.

RTO and RPO are closely related to the price of the solution, but of course the perfect solution is that both RTO and RPO are zero, which means that when the disaster occurs, the system recovers immediately and there is no data loss at all, but the cost is very expensive and is not necessarily necessary.

Therefore, the best solution must strike a balance between RTO,RPO, maintenance and price.

Especially for small and medium-sized enterprises, in the case of limited resources, they should first have a good understanding of the requirements for RTO and RPO, and then look at the price, which is easier to find and suitable for the enterprise.

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