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This article is to share with you about the level of disaster recovery backup in SHARE 78. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

The international standard SHARE 78 defines the disaster recovery system as seven levels, and the corresponding disaster recovery solutions of these seven levels are different in function and scope of application, so users' selection should be divided into different levels.

In the face of all kinds of possible disasters, enterprises need to conveniently and flexibly synchronize the data residing in different databases based on heterogeneous environment, so it is necessary to build a local and remote disaster recovery system that can resist or resolve all kinds of situations. But now, some computer information systems still lack the consideration of disaster recovery mechanism. many computer information systems only do simple different partitions of local disks or data backup of different disks on the same system. it is only a data backup system in a strict sense, which can not be called a disaster recovery system, such as the mirror backup, that is, file copy, which is commonly used in database systems. Based on the operating system file system replication: and based on the synchronization of data write operations between high-end online storage devices (disk arrays) and so on. In a general disaster, the integrity of data can be guaranteed in a certain sense, but it is difficult to ensure the reliability and security of user data, let alone provide transparent uninterrupted service to users.

Real disaster recovery must meet three elements: first, the components and data in the system are redundant, that is, when one system fails, the other system can maintain the smooth transmission of data; secondly, it has a long distance, because disasters always occur within a certain range, so a long distance can ensure that the data will not be completely destroyed by one disaster. Third, disaster recovery system should pursue omni-directional data replication, also known as disaster recovery "3R" (Redundance, Remote, Replication).

The definition of disaster recovery system in the international standard SHARE 78 has seven levels: from the simplest tape backup only locally, to storing the backed-up tape in different places, and then to establishing a remote backup system for real-time switching of the application system, the recovery time can also range from a few days to hours to minutes, seconds or zero data loss. At present, there are corresponding disaster recovery schemes for these seven levels, so when choosing disaster recovery schemes, users should focus on distinguishing their respective characteristics and scope of application, and judge which level to choose according to their own requirements for the disaster recovery system.

Level 0: backup the same way

The data of level 0 disaster recovery solution is only backed up locally, no data is backed up in different places, and there is no disaster recovery plan. This approach is the lowest-cost disaster recovery solution, but it does not have real disaster recovery capabilities.

In this disaster recovery scheme, the most commonly used is backup management software plus tape drive, which can be manually loaded tape drive or automatically loaded tape drive. It is the basis of all disaster recovery schemes, which are widely used from individual users to enterprise users. It is characterized by less user investment and simple technical implementation. The disadvantage is that in the event of a devastating local disaster, all local backup data will be lost and the business can not be recovered.

Level 1: remote backup

The first-level disaster recovery scheme is to back up the key data to the local tape media and then send it to the remote location for storage, but there is no available backup center, backup data processing system and backup network communication system, and there is no disaster recovery plan. After the disaster, use a new host to recover the data using remote data backup media (tape).

The cost of this scheme is low, and with the use of local backup management software, the backup data transported from different places can be restored to the local for business recovery after a devastating local disaster. But it is difficult to manage, that is, it is difficult to know what data is where, and the recovery time depends on when the hardware platform can be provided and ready. In the past, it was widely used by many large enterprises engaged in key business production as a means of disaster recovery in different places. At present, this level scheme is widely used in many small and medium-sized websites and users of small and medium-sized enterprises. For users who require rapid business recovery and massive data recovery, this scheme is not acceptable.

Level 2: hot backup site backup

The second-level disaster recovery scheme is to backup and store the key data in different places, make a corresponding disaster recovery plan, and have the ability of hot backup to recover the disaster. In the event of a disaster, the hot backup host system is used to recover the data. The difference between it and the level 1 disaster recovery scheme is that there is a hot backup site, which has a host system, and usually uses remote backup management software to back up the data transported to the remote data backup media (tape) to the host system. When a disaster occurs, you can quickly take over the application and resume production.

Due to the hot standby center, user investment will increase, and the corresponding managers will increase. The realization of the technology is simple, and using the hot backup system in different places, the business can be recovered quickly after the local devastating disaster. However, because the backup media is sent to different places by transportation, the data stored in the remote hot backup center is the last backup data, and the data may be lost for several days or even weeks. This cannot be tolerated for the disaster recovery of critical data.

Level 3: online data recovery

The third-level disaster recovery scheme is to backup and store the key data to different places through the network, with a corresponding disaster recovery plan, a backup center, and equipped with part of the data processing system and network communication system. This hierarchical scheme is characterized by using electronic data transmission instead of transportation to transmit backup data, thus improving the speed of disaster recovery. The data transmitted to the remote area through the network is backed up to the host system by using remote backup management software. Once a disaster occurs, the critical data can be quickly recovered through the network, and through network switching, the recovery time of critical applications can be reduced to one day or an hour. This hierarchical scheme has higher requirements for the network due to the continuous operation of the backup site, so the cost has increased accordingly.

Level 4: scheduled data backup

The fourth-level disaster recovery scheme is based on the third-level disaster recovery scheme, using backup management software to automatically backup part of the key data to different places through the communication network, and formulate the corresponding disaster recovery plan. In the event of a disaster, use the existing resources of the backup center and remote backup data to restore the operation of the key business system.

The characteristic of this level scheme is that the backup data is backed up to different places by automated backup management software, and the data saved by the remote hot backup center is the data that is backed up regularly, according to the different backup strategies, the time of data loss and recovery reaches the level of days or hours. Due to the high requirements for backup management software equipment and network equipment, the input cost will also increase. However, due to the characteristics of this level of backup, the business recovery time and the amount of data loss can not meet the requirements of key industries for critical data disaster recovery.

Level 5: real-time data backup

The level 5 disaster recovery scheme uses hardware mirroring technology and software data replication technology on the basis of the previous levels, that is to say, the data can be updated at both the application site and the backup site. The data is mirrored between the two sites and synchronized by remote asynchronous commits. Because key applications use dual online storage, only a small portion of the data is lost in the event of a disaster, and the recovery time is reduced to minutes or seconds. Due to the high requirements for storage systems and data replication software, the cost is also greatly increased.

This level of solution can not only ensure that it will not affect the progress of the current transaction, but also can copy the data generated by the transaction to other places in real time, so this level of solution is the most widely used at present, because of this, many manufacturers have disaster recovery solutions based on their own products. Such as remote data copy based on intelligent storage server introduced by storage manufacturer EMC, remote data replication based on system software provided by system replication software provider VERITAS, database replication scheme provided by database manufacturer Oracle and Sybase, etc. However, there is a deficiency in these schemes is that the remote backup data is in the state of Standby backup rather than real-time available data, so it takes a certain amount of time for business recovery after the disaster. More ideally, the backup site is not only a separate backup system, but also active and can provide production application services, so it can provide rapid business takeover, while backup data can be transferred in both directions. The time of data loss and recovery can reach minutes or even seconds. It is understood that the current global replication software of Goldengate can provide this function.

Level 6: zero data loss

Level 6 disaster recovery scheme is the most expensive and fastest way of disaster recovery, it is the highest level of disaster recovery, using a dedicated storage network to synchronously mirror critical data to the backup center, the data is not only confirmed locally, but also needs to be confirmed in different places (backup). Because the data is mirrored to the two sites, the remote disaster recovery system retains all the data and achieves zero data loss when the disaster occurs.

While all the local and remote data are updated, this scheme makes use of dual online storage and complete network switching ability, which not only ensures the complete consistency of data, but also has the automatic switching ability of applications in storage and network environments. In the event of a disaster, the backup site not only has all the data, but also the application can automatically take over to achieve zero data loss backup. Usually, redundant channels are provided in the connection of optical fiber devices in these two systems in case the working channel fails. Of course, due to the high requirements for storage system and storage system private network, the investment of users is huge. The users who adopt this way of disaster recovery are mainly large-scale enterprises and telecom-level enterprises with strong financial strength. However, in the process of practical application, because the mode of complete synchronization will have a great impact on the operation efficiency of the production system, it is suitable for key data systems with few production transactions or non-real-time transactions. At present, there are few users who adopt this level of disaster recovery scheme.

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