Resolving SQL Server Disk IO bottlenecks

--Analyze the queries that are currently running or which have recently ran and their plan is still in the cache.
SELECT dm_ws.wait_duration_ms,
dm_ws.wait_type,
dm_es.status,
dm_t.TEXT,
dm_qp.query_plan,
dm_ws.session_ID,
dm_es.cpu_time,
dm_es.memory_usage,
dm_es.logical_reads,
dm_es.total_elapsed_time,
dm_es.program_name,
DB_NAME(dm_r.database_id) DatabaseName,
-- Optional columns
dm_ws.blocking_session_id,
dm_r.wait_resource,
dm_es.login_name,
dm_r.command,
dm_r.last_wait_type
FROM sys.dm_os_waiting_tasks dm_ws
INNER JOIN sys.dm_exec_requests dm_r ON dm_ws.session_id = dm_r.session_id
INNER JOIN sys.dm_exec_sessions dm_es ON dm_es.session_id = dm_r.session_id
CROSS APPLY sys.dm_exec_sql_text (dm_r.sql_handle) dm_t
CROSS APPLY sys.dm_exec_query_plan (dm_r.plan_handle) dm_qp
WHERE dm_es.is_user_process = 1
GO
--You can change CROSS APPLY to OUTER APPLY if you want to see all the details which are omitted because of the plan cache

--All wait types since the server was last restarted, or the statistics were manually reset
WITH [Waits] AS
    (SELECT
        [wait_type],
        [wait_time_ms] / 1000.0 AS [WaitS],
        ([wait_time_ms] - [signal_wait_time_ms]) / 1000.0 AS [ResourceS],
        [signal_wait_time_ms] / 1000.0 AS [SignalS],
        [waiting_tasks_count] AS [WaitCount],
       100.0 * [wait_time_ms] / SUM ([wait_time_ms]) OVER() AS [Percentage],
        ROW_NUMBER() OVER(ORDER BY [wait_time_ms] DESC) AS [RowNum]
    FROM sys.dm_os_wait_stats
    WHERE [wait_type] NOT IN (
        N‘BROKER_EVENTHANDLER‘, N‘BROKER_RECEIVE_WAITFOR‘,
        N‘BROKER_TASK_STOP‘, N‘BROKER_TO_FLUSH‘,
        N‘BROKER_TRANSMITTER‘, N‘CHECKPOINT_QUEUE‘,
        N‘CHKPT‘, N‘CLR_AUTO_EVENT‘,
        N‘CLR_MANUAL_EVENT‘, N‘CLR_SEMAPHORE‘,
 
        -- Maybe uncomment these four if you have mirroring issues
        N‘DBMIRROR_DBM_EVENT‘, N‘DBMIRROR_EVENTS_QUEUE‘,
        N‘DBMIRROR_WORKER_QUEUE‘, N‘DBMIRRORING_CMD‘,
 
        N‘DIRTY_PAGE_POLL‘, N‘DISPATCHER_QUEUE_SEMAPHORE‘,
        N‘EXECSYNC‘, N‘FSAGENT‘,
        N‘FT_IFTS_SCHEDULER_IDLE_WAIT‘, N‘FT_IFTSHC_MUTEX‘,
 
        -- Maybe uncomment these six if you have AG issues
        N‘HADR_CLUSAPI_CALL‘, N‘HADR_FILESTREAM_IOMGR_IOCOMPLETION‘,
        N‘HADR_LOGCAPTURE_WAIT‘, N‘HADR_NOTIFICATION_DEQUEUE‘,
        N‘HADR_TIMER_TASK‘, N‘HADR_WORK_QUEUE‘,
 
        N‘KSOURCE_WAKEUP‘, N‘LAZYWRITER_SLEEP‘,
        N‘LOGMGR_QUEUE‘, N‘MEMORY_ALLOCATION_EXT‘,
        N‘ONDEMAND_TASK_QUEUE‘,
        N‘PREEMPTIVE_XE_GETTARGETSTATE‘,
        N‘PWAIT_ALL_COMPONENTS_INITIALIZED‘,
        N‘PWAIT_DIRECTLOGCONSUMER_GETNEXT‘,
        N‘QDS_PERSIST_TASK_MAIN_LOOP_SLEEP‘, N‘QDS_ASYNC_QUEUE‘,
        N‘QDS_CLEANUP_STALE_QUERIES_TASK_MAIN_LOOP_SLEEP‘,
        N‘QDS_SHUTDOWN_QUEUE‘, N‘REDO_THREAD_PENDING_WORK‘,
        N‘REQUEST_FOR_DEADLOCK_SEARCH‘, N‘RESOURCE_QUEUE‘,
        N‘SERVER_IDLE_CHECK‘, N‘SLEEP_BPOOL_FLUSH‘,
        N‘SLEEP_DBSTARTUP‘, N‘SLEEP_DCOMSTARTUP‘,
        N‘SLEEP_MASTERDBREADY‘, N‘SLEEP_MASTERMDREADY‘,
        N‘SLEEP_MASTERUPGRADED‘, N‘SLEEP_MSDBSTARTUP‘,
        N‘SLEEP_SYSTEMTASK‘, N‘SLEEP_TASK‘,
        N‘SLEEP_TEMPDBSTARTUP‘, N‘SNI_HTTP_ACCEPT‘,
        N‘SP_SERVER_DIAGNOSTICS_SLEEP‘, N‘SQLTRACE_BUFFER_FLUSH‘,
        N‘SQLTRACE_INCREMENTAL_FLUSH_SLEEP‘,
        N‘SQLTRACE_WAIT_ENTRIES‘, N‘WAIT_FOR_RESULTS‘,
        N‘WAITFOR‘, N‘WAITFOR_TASKSHUTDOWN‘,
        N‘WAIT_XTP_RECOVERY‘,
        N‘WAIT_XTP_HOST_WAIT‘, N‘WAIT_XTP_OFFLINE_CKPT_NEW_LOG‘,
        N‘WAIT_XTP_CKPT_CLOSE‘, N‘XE_DISPATCHER_JOIN‘,
        N‘XE_DISPATCHER_WAIT‘, N‘XE_TIMER_EVENT‘)
    AND [waiting_tasks_count] > 0
    )
SELECT
    MAX ([W1].[wait_type]) AS [WaitType],
    CAST (MAX ([W1].[WaitS]) AS DECIMAL (16,2)) AS [Wait_S],
    CAST (MAX ([W1].[ResourceS]) AS DECIMAL (16,2)) AS [Resource_S],
    CAST (MAX ([W1].[SignalS]) AS DECIMAL (16,2)) AS [Signal_S],
    MAX ([W1].[WaitCount]) AS [WaitCount],
    CAST (MAX ([W1].[Percentage]) AS DECIMAL (5,2)) AS [Percentage],
    CAST ((MAX ([W1].[WaitS]) / MAX ([W1].[WaitCount])) AS DECIMAL (16,4)) AS [AvgWait_S],
    CAST ((MAX ([W1].[ResourceS]) / MAX ([W1].[WaitCount])) AS DECIMAL (16,4)) AS [AvgRes_S],
    CAST ((MAX ([W1].[SignalS]) / MAX ([W1].[WaitCount])) AS DECIMAL (16,4)) AS [AvgSig_S],
    CAST (‘https://www.sqlskills.com/help/waits/‘ + MAX ([W1].[wait_type]) as XML) AS [Help/Info URL]
FROM [Waits] AS [W1]
INNER JOIN [Waits] AS [W2]
    ON [W2].[RowNum] <= [W1].[RowNum]
GROUP BY [W1].[RowNum]
HAVING SUM ([W2].[Percentage]) - MAX( [W1].[Percentage] ) < 95; -- percentage threshold
GO

-- reset statistics
DBCC SQLPERF (N‘sys.dm_os_wait_stats‘, CLEAR);
GO

-- Get I/O utilization by database (Query 31) (IO Usage By Database)
WITH Aggregate_IO_Statistics
AS
(SELECT DB_NAME(database_id) AS [Database Name],
CAST(SUM(num_of_bytes_read + num_of_bytes_written)/1048576 AS DECIMAL(12, 2)) AS io_in_mb
FROM sys.dm_io_virtual_file_stats(NULL, NULL) AS [DM_IO_STATS]
GROUP BY database_id)
SELECT ROW_NUMBER() OVER(ORDER BY io_in_mb DESC) AS [I/O Rank], [Database Name], io_in_mb AS [Total I/O (MB)],
       CAST(io_in_mb/ SUM(io_in_mb) OVER() * 100.0 AS DECIMAL(5,2)) AS [I/O Percent]
FROM Aggregate_IO_Statistics
ORDER BY [I/O Rank] OPTION (RECOMPILE);
-- Helps determine which database is using the most I/O resources on the instance

--下面的查询返回哪个数据库文件有最大的I/O延迟：
-- Calculates average stalls per read, per write,
-- and per total input/output for each database file.
SELECT DB_NAME(fs.database_id) AS [Database Name], mf.physical_name,
io_stall_read_ms, num_of_reads,
CAST(io_stall_read_ms/(1.0 + num_of_reads) AS NUMERIC(10,1)) AS
[avg_read_stall_ms],io_stall_write_ms,
num_of_writes,CAST(io_stall_write_ms/(1.0+num_of_writes) AS NUMERIC(10,1)) AS
[avg_write_stall_ms],
io_stall_read_ms + io_stall_write_ms AS [io_stalls], num_of_reads + num_of_writes
AS [total_io],
CAST((io_stall_read_ms + io_stall_write_ms)/(1.0 + num_of_reads + num_of_writes) AS
NUMERIC(10,1))
AS [avg_io_stall_ms]
FROM sys.dm_io_virtual_file_stats(null,null) AS fs
INNER JOIN sys.master_files AS mf WITH (NOLOCK)
ON fs.database_id = mf.database_id
AND fs.[file_id] = mf.[file_id]
ORDER BY avg_io_stall_ms DESC OPTION (RECOMPILE);
-- Helps determine which database files on
-- the entire instance have the most I/O bottlenecks

SELECT TOP 10
        t.text ,
        execution_count ,
        statement_start_offset AS stmt_start_offset ,
        sql_handle ,
        plan_handle ,
        total_logical_reads / execution_count AS avg_logical_reads ,
        total_logical_writes / execution_count AS avg_logical_writes ,
        total_physical_reads / execution_count AS avg_physical_reads,t.dbid
FROM    sys.dm_exec_query_stats AS s
        CROSS APPLY sys.dm_exec_sql_text(s.sql_handle) AS t
--WHERE    DB_NAME(t.dbid) = ‘AdventureWorks2008R2‘
ORDER BY avg_physical_reads DESC;