Query all database files that have potential disk bottlenecks

Overview

Microsoft generally recommends you disk io latency for sql server should average under 20ms for data and 15ms for Logs.

This query should show you all database files on your SQL Server instance that exceed the recommended thesholds.

According to SQL Server Central [http://www.sqlservercentral.com/articles/ssc+clinic/74097/]

• Less than 10 milliseconds (ms) = very good
• Between 10-20 ms = okay
• Between 20-50 ms = slow
• Greater than 50-100 ms = potentially serious IO bottleneck
• Greater than 100 ms = definite IO bottleneck

T-SQL Script

/*
 For SQL Versions older than 2012.. replace
sys.dm_io_virtual_file_stats(NULL, NULL)
with
sys.dm_io_virtual_file_stats(-1, -1)

*/
IF OBJECT_ID('tempdb..##dbFiles') IS NOT NULL 
    DROP TABLE ##dbFiles
GO

/* 
 table to hold all database files 
*/
CREATE TABLE ##dbFiles (
      DBName SYSNAME ,
      name VARCHAR(200) ,
      physical_name VARCHAR(2000) ,
      type_desc VARCHAR(200) ,
      state_desc VARCHAR(200) ,
      FILE_ID INT ) 
GO

/* 
 get all the database files for the sql instance
 into a table
*/
EXEC sp_msforeachdb 'use [?]
      insert into ##dbFiles
      select ''?'' as [DBName],name , physical_name,type_desc, state_desc,file_id
      from sys.database_files'

/*
 FIND FILES THAT HAVE UNACCEPTABLE DISK LATENCY
 AND JOIN TO DATABASE_FILES TABLE TO GIVE FRIENDLY NAMES
 THE VIRTUAL FILE STATS ARE FROM WHEN SQL SERVER WAS LAST RESTARTED

  > 20ms data and > 15ms logs
*/
DECLARE @DataReadLatency_ms INT,@DataWriteLatency_ms INT
DECLARE @LogReadLatency_ms INT,@LogWriteLatency_ms INT

SET @DataReadLatency_ms = 20
SET @DataWriteLatency_ms = 20
SET @LogReadLatency_ms = 15
SET @LogWriteLatency_ms = 15

SELECT  DB_NAME(database_id) AS 'db' ,
        df.file_id ,
        io_stall_read_ms / NULLIF(num_of_reads,0) AS 'AVG READ TRANSFER/SEC' ,
        io_stall_write_ms / NULLIF(num_of_writes,0) AS 'AVG WRITE TRANSFER/SEC' ,
        size_on_disk_bytes ,
        df.name ,
        df.physical_name ,
        df.type_desc
FROM    sys.dm_io_virtual_file_stats(NULL, NULL) stat
        JOIN ##dbFiles df ON stat.file_id = df.FILE_ID
                             AND df.DBName = DB_NAME(stat.database_id)
WHERE   num_of_reads > 0
        AND num_of_writes > 0
  -- ONLY INCLUDE UNACCEPTABLE LATENCY AND NOT DIV/0
        AND (( 
     ISNULL((io_stall_read_ms / NULLIF(num_of_reads,0)),0) > @DataReadLatency_ms AND type_desc = 'ROWS'
    OR 
              ISNULL((io_stall_write_ms / NULLIF(num_of_writes,0)),0) > @DataWriteLatency_ms AND type_desc = 'ROWS'
            )
   OR
   ( 
     ISNULL((io_stall_read_ms / NULLIF(num_of_reads,0)),0) > @LogReadLatency_ms AND type_desc = 'LOG'
    OR 
              ISNULL((io_stall_write_ms / NULLIF(num_of_writes,0)),0) > @LogWriteLatency_ms AND type_desc = 'LOG'
            ))
             
-- clean up
DROP TABLE ##dbFiles

Example of results returned by the script