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Merge pull request #20675 from taosdata/docs/wade-tolerance 

docs: refine the description about disaster recovery
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wade zhang 2023-03-28 17:04:52 +08:00 committed by GitHub
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12
docs/en/13-operation/03-tolerance.md
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@ -18,14 +18,8 @@ To achieve absolutely no data loss, set wal_level to 2 and wal_fsync_period to 0
## Disaster Recovery
TDengine uses replication to provide high availability.
TDengine provides disaster recovery by using taosX to replicate data between two TDengine clusters which are deployed in two distant data centers. Assume there are two TDengine clusters, A and B, A is the source and B is the target, and A takes the workload of writing and querying. You can deploy `taosX` in the data center where cluster A resides in, `taosX` consumes the data written into cluster A and writes into cluster B. If the data center of cluster A is disrupted because of disaster, you can switch to cluster to take the workload of data writing and querying, and deploy a `taosX` in the data center of cluster B to replicate data from cluster B to cluster A if cluster A has been recovered, or another cluster C if cluster A has not been recovered.
A TDengine cluster is managed by mnodes. You can configure up to three mnodes to ensure high availability. The data replication between mnode replicas is performed in a synchronous way to guarantee metadata consistency.
You can use the data replication feature of `taosX` to build more complicated disaster recovery solution.
The number of replicas for time series data in TDengine is associated with each database. There can be many databases in a cluster and each database can be configured with a different number of replicas. When creating a database, the parameter `replica` is used to specify the number of replicas. To achieve high availability, set `replica` to 3.
The number of dnodes in a TDengine cluster must NOT be lower than the number of replicas for any database, otherwise it would fail when trying to create a table.
As long as the dnodes of a TDengine cluster are deployed on different physical machines and the replica number is higher than 1, high availability can be achieved without any other assistance. For disaster recovery, dnodes of a TDengine cluster should be deployed in geographically different data centers.
Alternatively, you can use taosX to synchronize the data from one TDengine cluster to another cluster in a remote location. However, taosX is only available in TDengine enterprise version, for more information please contact tdengine.com.
taosX is only provided in TDengine enterprise edition, for more detail please contact business@tdengine.com.

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docs/zh/17-operation/03-tolerance.md
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@ -19,12 +19,8 @@ TDengine 接收到应用的请求数据包时，先将请求的原始数据包
## 灾备
TDengine 的集群通过多个副本的机制，来提供系统的高可用性，同时具备一定的灾备能力。
TDengine 灾备是通过在异地的两个数据中心中设置两个 TDengine 集群并利用 taosX 的数据复制能力来实现的。假定两个集群为集群 A 和集群 B，其中集群 A 为源集群，承担写入请求并提供查询服务。则在集群 A 所在数据中心中可以配置 taosX 利用 TDengine 提供的数据订阅能力，实时消费集群 A 中新写入的数据，并同步到集群 B。如果发生了灾难导致集群 A 所在数据中心不可用，则可以启用集群 B 作为数据写入和查询的主节点，并在集群 B 所处数据中心中配置 taosX 将数据复制到已经恢复的集群 A 或者新建的集群 C。
TDengine 集群是由 mnode 负责管理的，为保证 mnode 的高可靠，可以配置 三个 mnode 副本。为保证元数据的强一致性，mnode 副本之间通过同步方式进行数据复制，保证了元数据的强一致性。
利用 taosX 的数据复制能力也可以构造出更复杂的灾备方案。
TDengine 集群中的时序数据的副本数是与数据库关联的，一个集群里可以有多个数据库，每个数据库可以配置不同的副本数。创建数据库时，通过参数 replica 指定副本数。为了支持高可靠，需要设置副本数为 3。
TDengine 集群的节点数必须大于等于副本数，否则创建表时将报错。
当 TDengine 集群中的节点部署在不同的物理机上，并设置多个副本数时，就实现了系统的高可靠性，无需再使用其他软件或工具。TDengine 企业版还可以将副本部署在不同机房，从而实现异地容灾。
taosX 只在 TDengine 企业版中提供，关于其具体细节，请联系 business@taosdata.com