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所在平台: Udemy |
课程主页: https://www.udemy.com/course/microsoft-sql-server-alwayson-ha-solution/
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本课程“学习 Microsoft SQL Server AlwaysOn HA 解决方案”旨在教授学员如何设置、配置和监控 Microsoft SQL Server 的 AlwaysOn 功能。 AlwaysOn 可用性组（SQL Server AlwaysOn Availability Groups）是 SQL Server 中一项重要的容错功能，它支持一组用户数据库（称为可用性数据库）作为一个整体进行故障转移。一个可用性组包含一个主副本，负责托管主数据库，以及最多八个辅助副本，每个辅助副本负责托管一套对应的辅助数据库，并作为可用性组潜在的故障转移目标。 需要理解的关键点包括： * **故障转移单位**：可用性组以可用性副本为单位进行故障转移。 * **冗余级别**：可用性副本提供的是数据库级别的冗余。 * **数据同步**：主副本通过日志记录将事务日志记录发送到每个辅助数据库。辅助副本会缓存（硬化日志）这些事务日志记录，然后将其应用到各自的辅助数据库。数据同步独立发生在主数据库和每个连接的辅助数据库之间。 * **读取能力**：学员可以配置某些辅助副本支持只读访问，并允许在辅助副本上执行备份操作。 * **依赖项**：部署 AlwaysOn 可用性组需要一个 Windows Server 故障转移群集（WSFC）集群。每个可用性副本必须位于同一个 WSFC 群集的不同节点上。 * **WSFC 集群集成**：每个可用性组都会创建相应的 WSFC 资源组，WSFC 集群会监控该资源组以评估主副本的健康状况。 * **仲裁**：WSFC 集群的仲裁基于所有节点，与节点是否托管可用性副本无关。与数据库镜像不同，AlwaysOn 可用性组没有见证角色。 总而言之，本课程为学习者提供了构建和管理 SQL Server 高可用性解决方案所需的知识和技能，特别侧重于 AlwaysOn 可用性组的配置和操作。
Learn how to Setup,Configure and Monitor Microsoft SQL Server AlwaysOn feature. Always On Availability Groups (SQL Server). An availability group supports a failover environment for a discrete set of user databases, known as availability databases, that fail over together. An availability group supports a set of primary databases and one to eight sets of corresponding secondary databases. Secondary databases are not backups. Continue to back up your databases and their transaction logs on a regular basis. Each set of availability database is hosted by an availability replica. Two types of availability replicas exist: a single primary replica. which hosts the primary databases, and one to eight secondary replicas, each of which hosts a set of secondary databases and serves as a potential failover targets for the availability group. An availability group fails over at the level of an availability replica. An availability replica provides redundancy only at the database level-for the set of databases in one availability group. Failovers are not caused by database issues such as a database becoming suspect due to a loss of a data file or corruption of a transaction log. The primary replica makes the primary databases available for read-write connections from clients. Also, in a process known as data synchronization, which occurs at the database level. The primary replica sends transaction log records of each primary database to every secondary database. Every secondary replica caches the transaction log records (hardens the log) and then applies them to its corresponding secondary database. Data synchronization occurs between the primary database and each connected secondary database, independently of the other databases. Therefore, a secondary database can be suspended or fail without affecting other secondary databases, and a primary database can be suspended or fail without affecting other primary databases. Optionally, you can configure one or more secondary replicas to support read-only access to secondary databases, and you can configure any secondary replica to permit backups on secondary databases. Deploying Always On Availability Groups requires a Windows Server Failover Clustering (WSFC) cluster. Each availability replica of a given availability group must reside on a different node of the same WSFC cluster. The only exception is that while being migrated to another WSFC cluster, an availability group can temporarily straddle two clusters. A WSFC resource group is created for every availability group that you create. The WSFC cluster monitors this resource group to evaluate the health of the primary replica. The quorum for Always On Availability Groups is based on all nodes in the WSFC cluster regardless of whether a given cluster node hosts any availability replicas. In contrast to database mirroring, there is no witness role in Always On Availability Groups.
