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FusionStorage V100R006C30 Block Storage Service Disaster Recovery Feature Guide 03

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Basic Concepts

Basic Concepts

This section describes basic concepts involved in the disaster recovery feature.

DR Node

DR nodes are used for data replication between sites, and therefore they are required for both local and remote sites. DR nodes can be deployed on either physical servers or VMs.

The DR service can be deployed on an independent node or a storage node. That is, a DR node can be either independently deployed or co-deployed with a storage node.

DR Cluster

A DR cluster is a group of DR nodes. It consists of a control cluster and a service cluster. The control cluster manages all DR nodes, and the service cluster manages the services.

CM: Cluster Management manages information of the control cluster.


The DR cluster metadata includes the DR cluster management data information and user management data information.
  • ZK: ZooKeeper specifies the control cluster metadata, which stores the control cluster information, such as information about DR nodes and cluster views.
  • CCDB: Cluster Configuration Data Base specifies the service cluster metadata, which stores the service cluster information, such as information about HyperMetro pairs, remote replication pair and consistency groups.

Address Pool

An address pool is used to establish the links between DR nodes at the two sites. It consists of the replication plane IP addresses of the local DR nodes that need to communicate with the remote DR nodes.

Local Volume and Remote Volume

The volume in the storage system at the local data center is called the local volume, and the volume in the storage system at the remote data center is called the remote volume.


A pair indicates an active-active relationship between a local volume and a remote volume. A local volume and a remote volume form a pair.

Consistency Group

A consistency group is a collection of pairs that have service relationships with one another. For example, the local storage system has three local volumes that respectively store the service data, logs, and change tracking information of a database. If the data on any of the three volumes becomes invalid, all data on these volumes becomes unavailable. pairs containing these three volumes form a consistency group. In the actual configuration, you need to create a consistency group first and then add these pairs to the group.


Dual-write is a concept of HyperMetro. Dual-write enables I/O requests of an application host to be written into both the local volume and remote volume at the same time.


Data change log (DCL) is a concept of HyperMetro. DCLs record data changes between the two storage systems.

HyperMetro Domain

HyperMetro domain is a concept of HyperMetro. A HyperMetro domain consists of local devices, remote devices, and a quorum server. Application hosts can access data across data centers using a HyperMetro domain.

Preferred Site Switch

The preferred site takes precedence during arbitration. If a link fault occurs, the preferred site wins the arbitration and continues providing services for hosts.

When a HyperMetro pair is created, the local storage system is by default the preferred site and the remote storage system is the non-preferred site.

Primary Volume and Secondary Volume

Primary volume and secondary volume are concepts of remote replication. The volume that plays the primary role in a remote replication pair is called a primary volume and that plays the secondary role in a remote replication pair is called a secondary volume.


Split in remote replication is the same as suspension in HyperMetro. It refers to the process of temporarily suspending the remote replication relationship between local volumes and remote volumes.

Protection for Secondary Resources

Protection for secondary resources is a concept of remote replication. It refers that data of secondary volumes can be read but cannot be written.

Updated: 2019-01-17

Document ID: EDOC1100044928

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