SQL Server 2012 notes Sharing-7: Enhancements to High availability features

(i) Database mirroring

1, support compression transmission

2. Support automatic page repair (msdb: suspect_pages)

(ii) Database cluster

1, support multi-subnet

A SQL Server multi-subnet failover cluster is a configuration in which each failover cluster node is connected to another subnet or other subnet group. These subnets can be in the same location, or they can be in geographically dispersed sites. Clustering across geographically dispersed sites is sometimes called a stretch cluster set. Because there is no shared storage that can be accessed by all nodes, data should be replicated between data stores on multiple subnets. For data replication, there is more than one copy of the available data. As a result, a multi-subnet failover cluster provides a disaster recovery solution in addition to high availability.

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Deployment reference: http://technet.microsoft.com/zh-cn/library/ff878716 (v=sql.110). aspx

2. More flexible Failover strategy (failureconditionlevel)

In a SQL Server failover cluster instance, only one node can have a cluster resource group at a given time. The system supports client requests through this failover cluster instance's node. In the event of a failover, ownership of the group is transferred to another node in the failover cluster. This process is known as failover. A more flexible failover strategy can be configured with improved fault detection introduced in SQL Server 2012 and the addition of fault condition level properties.

Deployment reference: http://technet.microsoft.com/zh-cn/library/ff878664 (v=sql.110). aspx

3. Support tempdb on Local disk

For SQL Server failover cluster installations of tempdb, the local disk is now a supported storage option.

(iii) AlwaysOn

AlwaysOn on a SQL Server 2012 platform can support 5 nodes for read-write separation.

For example: Three node database, one node write, one node read (report service), one node backup.

SQL Server 2012 currently only has read-write separations, and there is no fully-loaded, high-availability mode with load balancing (such as Oracle RAC).

If the cluster node is an odd number, the quorum disk is not required and the quorum disk is required if it is an even number.

Cluster of a/a mode

SERVER01:INSTANCE01 Active INSTANCE02 Passive

SERVER02:INSTANCE01 Passive INSTANCE02 Active

AlwaysOn incorporates the benefits of failover clustering and mirroring, with the underlying technology of failover clustering to support read-write separation and geo-disaster replication.

1. Multiple databases support failover

2. A read replica node (with read-only connection access, a read-only connection to the replica can access and read its database while this replica is running as a secondary replica.) & #160; ) & #160;
3. Support Synchronous and asynchronous (asynchronous commit mode). This availability mode is a disaster recovery solution that is suitable for situations where the availability replicas are distributed far away. Synchronous commit mode. This availability mode emphasizes high availability and data protection in relation to performance, at the expense of increased transaction latency. ）
4. Backup and DBCC CheckDB on the replica node (when the replica is running as a secondary replica, perform a back-up operation on the replica's database. By using Active Accessibility, you can better leverage your secondary hardware resources to improve IT efficiency and reduce costs. In addition, by transferring the read-intent application and the backup job to the secondary replica, you can improve performance against the primary replica. ）
5. Automatic page Repair

Reference: http://543925535.blog.51cto.com/639838/1341805

6. Cross-cluster migration of ALWAYSON availability groups for operating system upgrades

SQL Server SP1 introduces support for cross-cluster migrations of AlwaysOn availability groups for deployment to a new Windows Server failover cluster (WSFC) cluster. Cross-cluster migration moves an AlwaysOn availability group or a batch of availability groups to the new target WSFC cluster, with the shortest amount of downtime. Through the cross-cluster migration process, you can maintain your service level agreements (SLAs) when you upgrade to a Windows Server 2012 cluster. SQL Server SP1 must be installed and enabled for AlwaysOn on the target WSFC cluster. The success of cross-cluster migration depends on the detailed planning and preparation of the target WSFC cluster.

Reference: http://msdn.microsoft.com/zh-CN/library/jj873730.aspx

7. Flexible and highly available solutions

Supports local direct-attached storage and supports shared storage

Supports synchronous data replication and asynchronous data replication

This article from "Zeng Hung Xin Technical column" blog, declined to reprint!