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[AlwaysOn] AlwaysOn可用性组的故障转移和故障转移模式[中英文对照] 1

原创 SQL Server 作者:cow977 时间:2019-08-24 08:02:54 0 删除 编辑

在可用性组的上下文中,可用性副本的主角色和辅助角色在称为“故障转移”的过程中通常是可互换的。存在三种故障转移形式:自动故障转移(无数据丢失)、计划的手动故障转移(无数据丢失)和强制手动故障转移(可能丢失数据)。最后一种形式通常称为“强制故障转移”。自动故障转移和计划的手动故障转移会保留您的所有数据。可用性组在可用性副本级别进行故障转移。也就是说,可用性组故障转移到其次要副本之一(当前故障转移目标)。

Within the context of an availability group, the primary role and   secondary role of availability replicas are typically interchangeable in a   process known as failover. Three forms of failover exist: automatic   failover (without data loss), planned manual failover (without data loss), and   forced manual failover (with possible data loss), typically called forced   failover. Automatic and planned manual failover preserve all your data. An   availability group fails over at the availability-replica level. That is, an   availability group fails over to one of its secondary replicas (the current failover   target).

备注

Remarks

在数据库级别,诸如因数据文件丢失而使数据库成为可疑数据库、删除数据库或事务日志损坏之类的数据库问题不会导致可用性组进行故障转移。

Issues at the database level, such as a database becoming suspect due to   the loss of a data file, deletion of a database, or corruption of a   transaction log, do not cause an availability group to failover.

在故障转移期间,故障转移目标将接管主角色、恢复其数据库并且使它们作为新的主数据库处于联机状态。以前的主副本一旦可用将切换为辅助角色,并且其数据库成为辅助数据库。在可能的情况下,这些角色可以来回切换(或切换为不同的故障转移目标),以应对多次故障或满足管理的需要。

During the failover, the failover target takes over the primary role,   recovers its databases, and brings them online as the new primary databases. The   former primary replica, when available, switches to the secondary role, and   its databases become secondary databases. Potentially, these roles can switch   back and forth (or to a different failover target) in response to multiple   failures or for administrative purposes.

故障转移模式”属性指定某一给定可用性副本支持的故障转移形式。对于某一给定的可用性副本,可能的故障转移模式取决于该副本的 可用性模式,如下所示:

The form(s) of failover that a given availability replica supports is   specified by the failover mode property.For a given availability   replica, the possible failover modes depends on the availability   mode of the replica, as follows:

·        同步提交副本支持两种设置:自动或手动。“自动”设置支持自动故障转移和手动故障转移。为了防止丢失数据,自动故障转移和计划的故障转移要求故障转移目标为同步提交的辅助副本且处于正常同步状态(这表示故障转移目标上的每个辅助数据库与相应的主数据库同步)。只要某一辅助副本不满足这两个条件,它就仅支持强制故障转移。请注意, 强制故障转移还支持角色处于“正在解析”状态的副本

·        Synchronous-commit replicas support two settings-automatic or manual. The   "automatic" setting supports both automatic failover and manual   failover. To prevent data loss, automatic failover and planned failover   require that the failover target be a synchronous-commit secondary replica   with a healthy synchronization state (this indicates that every secondary   database on the failover target is synchronized with its corresponding   primary database). Whenever a secondary replica does not meet both of these   conditions, it supports only forced failover. Note that forced failover is   also supported a replicas whose role is in the RESOLVING state.

·        异步提交副本 仅支持手动故障转移模式。此外,因为它们永远不会同步,所以它们仅支持强制故障转移。

·        Asynchronous-commit replicas support only the manual failover mode. Moreover,   because they are never synchronized, they support only forced failover.

备注

Remarks

故障转移后,需要访问主数据库的客户端应用程序必须连接到新的主副本。此外,如果新的辅助副本配置为允许只读访问,则只读客户端应用程序可以连接到它。有关客户端如何连接到可用性组的信息,请参阅 可用性组侦听程序、客户端连接和应用程序故障转移(SQL Server)

After a failover, client applications that need to access the primary   databases must connect to the new primary replica. Also, if the new secondary   replica is configured to allow read-only access, read-only client   applications can connect to it. For information about how clients connect to   an availability group, see Availability   Group Listeners, Client Connectivity, and Application Failover(SQL Server).


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