Differences between disaster recovery and backup

Disaster tolerance: when the above disasters occur, the business of the survival system is kept running continuously under the condition that the data of the production system is minimized.

Fault tolerance: refers to the ability to ensure that the computer system can still work when the software and hardware of the computer system fail.

Difference: fault tolerance can be realized through hardware redundancy, error checking, hot switching and special software, while disaster tolerance must be realized through system redundancy, disaster detection, system migration and other technologies. When the equipment fault can not be solved by the fault-tolerant mechanism, resulting in system downtime, the solution of this fault belongs to the category of disaster tolerance.

Disaster recovery: refers to the ability to restore the system to normal operation after a disaster.

Difference: disaster recovery emphasizes the ability to ensure the continuous and uninterrupted operation of the system business in the event of a disaster, while disaster recovery emphasizes the ability to recover the system after a disaster. The current disaster recovery systems all contain the function of disaster recovery, so the discussion in this paper includes not only the content of disaster recovery, but also some content of disaster recovery.

The disaster recovery system provides a fairly high guarantee of data security in enterprises, but what is the disaster recovery system and what do they mean?I’m afraid even the network administrator who is using disaster recovery backup can’t explain. This article uses the most simple language to explain what disaster recovery backup is.

Different purposes

The purpose of the disaster recovery system is to ensure that the system data and services are “linear”, 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 disaster recovery backup technology is different. Backup is “the process of transferring online data to offline data”, and its purpose is to deal with logical errors in system data and historical data storage.

Therefore, today, when various fault-tolerant technologies are very abundant, the backup system is still irreplaceable.

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 to prevent data loss caused by system errors or system failures. Backup is the last line of defense for high availability of data. Its purpose is to recover data in case of system data crash.

Disaster recovery is indispensable

If the backup system is built, does it not need a disaster recovery backup system?It also depends on the expected value of the business department for RTO (time index required for recovery) /rpo (latest state that can be recovered). If the 1TB database RTO = 8 hours and RPO = 1 day are allowed, the backup system can meet the requirements. At the same time, the purpose of backup is to deal with logical errors in system data and save historical data. It can only meet the data recovery purpose in case 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 businesses. When people talk about disaster recovery backup, they often aim at the fact that when the production system cannot work normally, its business can be replaced by the disaster recovery system to continue to work normally.

Provide good RTO and RPO indicators. At the same time, the remote disaster recovery system has the ability to cope with various disasters, especially regional and devastating disasters, and has relatively perfect data protection and disaster recovery functions to ensure the integrity of data and business continuity when a disaster strikes, and restore the normal operation of the business system in the shortest time to minimize the loss.

Disaster recovery cannot replace backup

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

Factors considered in planning enterprise safety assurance system

For enterprises, how to build their own disaster recovery system, whether to build only the backup system, or only the disaster recovery system, or whether they need to build both at the same time, or step-by-step construction, which comes first and which comes later, depends mainly on business needs:

Types of disasters to be prevented:

The types of disasters that the enterprise information system may encounter and their proportions are as follows:

For “human error”, “software damage and program error” plus “virus”, these are called logic errors, accounting for 56% of the total failures. These errors can only be prevented through the backup system;

“Hardware and system failures” and “natural disasters” can be prevented in the disaster recovery system (or remote backup), accounting for 44% of the total failure rate.

Allowed RTO and RPO metrics

Technically, there are two main indicators to measure the disaster recovery system: RPO (recovery point object) and RTO (recovery time object), where RPO represents the amount of data allowed to be lost when a disaster occurs; RTO represents the time of system recovery.

Generally speaking, the disaster recovery system can provide better RTO and RPO indicators.

System investment

In general, the investment in the construction of backup system is much smaller than that in the construction of standard disaster recovery system:

The investment scale of backup system is generally millions;

The most economical set of disaster recovery system investment will be tens of millions;

Common disaster recovery combinations

Based on the above reasons, the industry generally adopts the following methods in the construction of disaster recovery system:

Build a local backup system in the computer room

Build remote backup system

In this way, the price of the backup system can meet the backup and remote disaster recovery functions, and can avoid data loss caused by earthquake, fire or other disasters in the main production center.

Backup system + Remote Disaster Recovery System.

This is an ideal integrated solution for disaster recovery system, which can avoid all possible errors to a great extent.

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