What does off-site disaster recovery backup mean?

What does off-site disaster recovery backup mean?

Off-site disaster recovery backup, as the name suggests, is to build one or more sets of the same application or database in different regions to take over immediately after a disaster. This method plays a role in enterprise applications and databases. It plays a role in security, business continuity and other aspects.

Advantages of off-site disaster recovery backup

1. Centralized storage. Online real-time backup is usually adopted, which not only improves the administrator's work efficiency, but also reduces the need for complex equipment.

2. Centralized management. Take Xirui's off-site disaster recovery solution as an example. It enables users to implement real-time management and overall system strategies. Network administrators can use browsers to manage data storage, eliminating the need to complete a large amount of repetitive work.

3. Strong interoperability. Among the off-site disaster recovery solutions of various manufacturers, most of them can integrate different heterogeneous storage environments, that is, they can use existing storage devices and support multiple storage architectures such as NAS, IP SAN, and FC SAN.

Off-site disaster recovery backup function

1. Remote mirroring technology

Remote mirroring technology is the data between the main data center and the backup center Used for backup. Remote mirroring, also called remote replication, is the core technology of disaster recovery and backup. It is also the basis for maintaining remote data synchronization and achieving disaster recovery. Remote mirroring can be divided into synchronous remote mirroring and asynchronous remote mirroring based on whether the host requesting mirroring requires confirmation information from the remote mirroring site.

Synchronous remote mirroring (synchronous replication technology) refers to using remote mirroring software to copy local data to a remote location in a completely synchronous manner. Each local I/O transaction needs to wait for the completion confirmation of remote replication. , and then be released. Synchronous mirroring enables remote copies to always match what the local machine requires to be copied. When the primary site fails and the user's application is switched to the backup alternative site, the mirrored remote copy can ensure that the business continues to execute without data loss. However, it has the disadvantage of long delay caused by round-trip propagation, and is limited to applications at relatively short distances.

Asynchronous remote mirroring (asynchronous replication technology) ensures that basic I/O operations to the local storage system are completed before updating the remote storage view, and the I/O operation completion confirmation provided by the local storage system to the requesting mirror host information. Remote data replication is performed in a background synchronization manner, which has little impact on local system performance, long transmission distance (up to more than 1,000 kilometers), and low network bandwidth requirements. However, many writes to remote slave storage subsystems are not acknowledged, and when some factor causes data transfer to fail, data consistency issues may arise. To solve this problem, the data is updated.

2. Snapshot technology

Remote mirroring technology is often combined with snapshot technology to achieve remote backup, that is, data is backed up to a remote storage system through mirroring, and then snapshot technology is used to back up the data in the remote storage system. The information is backed up to remote tape libraries and optical disk libraries.

Snapshot uses software to quickly scan the data of the disk subsystem to be backed up, and establishes a snapshot logical unit number LUN and snapshot cache of the data to be backed up. During the quick scan, the data that will be modified during the backup process is Data blocks are quickly copied to the snapshot cache at the same time. A snapshot LUN is a set of pointers that point to unchanged data blocks in the snapshot cache and disk subsystem (during the backup process). While normal business is going on, the snapshot LUN is used to achieve a complete backup of the original data. It allows users to extract current online business data in real time without affecting normal business. Its "backup window" is close to zero, which can greatly increase the continuity of system business and provide a guarantee for realizing the true 7×24 operation of the system.

Snapshot uses memory as a buffer (snapshot cache), and the snapshot software provides an instant data image stored on the system disk. It has a buffer scheduling problem.

3. Interconnection technology

The early data backup between the primary data center and the backup data center was mainly SAN-based remote replication (mirror), that is, through Fiber Channel FC. Connect two SANs for remote mirroring (replication). When a disaster occurs, the backup data center replaces the primary data center to ensure the continuity of system operations. This remote disaster recovery and backup method has some shortcomings, such as high implementation cost, poor interoperability of equipment, and short geographical distance (10 kilometers). These factors hinder its further promotion and application.

A variety of remote data disaster recovery and backup technologies based on IP SAN. They use the IP-based SAN interconnection protocol to remotely copy the information in the main data center SAN to the backup center SAN through the existing TCP/IP network. When the amount of data stored in the backup center is too large, snapshot technology can be used to back it up to a tape library or optical disk library. This IP-based SAN remote disaster recovery backup can span LAN, MAN and WAN. It has low cost, good scalability and broad development prospects. IP-based interconnection protocols include: FCIP, iFCP, Infiniband, iSCSI, etc.

4. Virtual storage

In some disaster recovery solution products, virtual storage technology is also adopted, such as Xirui's remote disaster recovery solution. Virtualized storage technology has created a new situation in system flexibility and scalability. It cascades several different storage devices such as IDE or SCSI drives into a storage pool. The entire storage capacity of a storage cluster can be divided into multiple logical volumes and managed as virtual partitions. Storage thus becomes a function rather than a physical property, which is a major limitation of server-based storage architectures.

The virtual storage system also provides the function of dynamically changing the size of logical volumes. In fact, the capacity of a storage volume can be increased or decreased at will online. You can change the size of logical volumes in a cluster by adding or reducing the number of physical disks in the system. This feature allows the volume's capacity to dynamically change with immediate user requirements. In addition, storage volumes can be easily resized, moved and replaced. When you install the system, allocate only the minimum capacity to each logical volume and leave the remaining space on the disk. As your business grows, you can use the remaining space to expand the logical volume as needed. You can also move data online from the old drive to the new drive without interrupting service.

A key advantage of storage virtualization is that it allows heterogeneous systems and applications to share storage devices regardless of where they are located. Companies will no longer need to attach a tape device to each branch server.

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