SQL Server Availability Group Failover 测试

兼容性测试:

测试脚本:

环境：windows failover cluster

主库执行脚本：

USE [master]
GO
ALTER AVAILABILITY GROUP [test_AG]
MODIFY REPLICA ON N'host1' WITH (FAILOVER_MODE = AUTOMATIC)
GO

报错:
Msg 35215, Level 16, State 17, Line 3
The Alter operation is not allowed on availability replica 'UELT1WASFSD01VS', because automatic failover mode is an invalid configuration on a SQL Server Failover Cluster Instance. Retry the operation by specifying manual failover mode.

结果证明AG 自动failover的属性和windows failover cluster不兼容，如果要启用AG自动failover必须使用单实例模式的sql server.

2.AG自动failover功能测试

测试1:
在sscm中手动停止主库sql service，观察是否自动failover到备库。

测试2：

直接关闭主库所在的主机，观察是否failover到备库

测试1和测试2均实现自动failover。

在failover期间，会有应用程序连接拒绝出现:

11/01/19 06:04:10.368 [0x00003688] [spid 769] SQLState: 08S01, Native Error: 10054, Severity: 0, State: 10, Line: 0
[Microsoft][SQL Server Native Client 11.0]TCP Provider: An existing connection was forcibly closed by the remote host.

3.AG Failover性能测试
table: 5218283 rows clustered.
query: select count(*) from test
command:.\ostress -Suedv1wasfsdba01 -dtest -E -Q"select count(*) from dbo.test" -ooutput -mstress -n500 -r100 -T10 -T88 -T146

Primary Session number	Secondary session number	1st Failover time(s)	2nd Failover time(s)	3rd Failover time(s)
300	0	5	5	5
0	300	25	25	23
500	0	5	5	5
0	500	44	46	31
1000	0	5	5	5
0	1000	89	88	91

session 1000的时候，客户端报连接超时错误:
解决方案：
exec sp_configure 'max worker threads',4096
go
reconfigure

总结:

1.Avalibility group 自动failover 和 FCI failover不兼容，只能应用于 standalone instance.

2.Avalibility group automatic failover 执行sql service 宕机 failover and 主机宕机 failover.

3. failover 时间取决于备库上只读会话并发数目，可以降低主要备库上的只读负载，而在非主要备库上执行只读负载的方式来降低failover的时间。