Help: SQL Server

Reading theory is important but doing practical in real life helps remembering a concept for longer time. In last post about resource governor, we have learned the basics. In this blog, we would see resource governor in action. If you have SQL Server 2014 installed then you can easily follow the steps and copy/paste the scripts. As a demo, we would create two resource groups and pools which different settings.

Step 1: Create Resource Pools

As a first step, we would create resource pool for limiting IO done by a specific pool. ThousandIOPs sets the maximum I/Os per second (IOPS) to 1000 and TenIOPs sets maximum IOPS to 10. This is done via parameter MAX_IOPS_PER_VOLUME.

CREATE RESOURCE POOL [ThousandIOPs] WITH
(
    MAX_IOPS_PER_VOLUME = 1000
)
GO
CREATE RESOURCE POOL [TenIOPs] WITH
(
    MAX_IOPS_PER_VOLUME = 10
)
GO

Step 2: Create Workload Groups tied to resource pool

In below code I created Resource Groups named “FastIO” and “SlowIO” and associated them with my Resource Pool named “ThousandIOPs” and “TenIOPs” respectively.

-- Create a  Workload Group for FastIO 
CREATE WORKLOAD GROUP [FastIO]
USING [ThousandIOPs]
GO
-- Create a new Workload Group for throttled IO
CREATE WORKLOAD GROUP [SlowIO]
USING [TenIOPs]
GO

Step 3: Define a classifier function to bind request to workgroup

In Step 3, I need to define a classifier function that will identify the resource group to which request should be categorized. You can notice that I have used SUSER_NAME() function to get resource group name as output parameter. In other words, if use SlowIO logs in, he would be bound to group SlowIO and hence tied to TenIOPs.

-- Create a Classifier Function for Resource Governor
Use Master
GO
CREATE FUNCTION dbo.MyClassifierFunction()
RETURNS SYSNAME WITH SCHEMABINDING
AS
BEGIN
    DECLARE @GroupName SYSNAME
    
    IF SUSER_NAME() = 'SlowIO'
    BEGIN
        SET @GroupName = 'SlowIO'
        RETURN @GroupName;
    END
    ELSE IF SUSER_NAME() = 'FastIO'
    BEGIN
        SET @GroupName = 'FastIO'
        RETURN @GroupName;
    END
    ELSE 
    BEGIN
        SET @GroupName = 'Default'
    END    
    RETURN @GroupName;
END
GO

Step 4: Register classifier_function to resource governor

So far we have setup Resource Governor to control I/O. We need to do one last thing.  We need to alter Resource Governor to use classifier function, defined in step3, and then reconfigure it to use all my new settings.  This can be done by running the following code:

-- Register the Classifier Function within Resource Governor
ALTER RESOURCE GOVERNOR WITH
(
    CLASSIFIER_FUNCTION = dbo.MyClassifierFunction
)
GO
-- Reconfigure resource governor
ALTER RESOURCE GOVERNOR RECONFIGURE
GO

Testing IO Resource Governor

To test resource governor, we will create two logins SlowIO and FastIO and they would be falling into different pools TenIOPs and ThousandIOPs respectively. I have given sysadmin rights for simplicity of demo.

Create login SlowIO with password = 'pass@word1'
GO
Create login FastIO with password = 'pass@word1'
GO
ALTER SERVER ROLE [sysadmin] ADD MEMBER [SlowIO]
GO
ALTER SERVER ROLE [sysadmin] ADD MEMBER [FastIO]
GO

Create database, table and populate data using below script.

CREATE DATABASE rgiotest 
go 
USE rgiotest; 
go 
CREATE TABLE iotest 
  ( 
     id             INT IDENTITY  CONSTRAINT [PK_IOTest_ID] PRIMARY KEY CLUSTERED (id ASC), 
     iintegercolumn INT, 
     ccharcolumn    CHAR(50) 
  ); 
go 
SET nocount ON; 
INSERT INTO iotest 
            (iintegercolumn, 
             ccharcolumn) 
SELECT TOP (20000) Row_number() 
                     OVER( 
                       ORDER BY a.object_id), 
                   'X'
FROM   sys.all_columns AS a 
       CROSS JOIN sys.all_columns AS b
go 100 -- this would run above insert 100 times

Above script took around 30 seconds on my laptop. Now, I would run the script to do a lots of read using two different logins.

CHECKPOINT
DBCC DROPCLEANBUFFERS

USE RGIOTEST;
GO
IF OBJECT_ID ('tempdb..#IOTest') is not null
   DROP TABLE #IOTest;
GO
SELECT top 2000000 * INTO #IOTest FROM IOTest;
GO

I have used DROPCLEANBUFFERS in above script because I don’t want SQL to read data from memory but do a physical IO.

Logged in using SlowIO account

Script has taken 37 seconds and below is the perfmon counters which I have spoken in last blog.

The value is throttled to around 10 which is what we have capped (MAX_IOPS_PER_VOLUME = 10)

Logged into using FastIO account

Here the same query executed in 4 seconds.

The value is much under control. We have capped to 1000 and we are much under limits.

I must say that the demo shown here is extremely simple, but you can must have got an understanding about you how to setup and use the Resource Governor to throttle IO in SQL Server 2014.

Hope you are learning something new about SQL Server 2014 from this series.