Determine Free Disk Space in SQL Server with T-SQL Code

Problem
At our organization we need to check for a minimum amount of free space before proceeding with some processes that run on SQL Server 2000, 2005 and 2008 SQL Server instances. Do you know of a way to find out the free disk space and then fail the process if it does not meet the minimum requirements? Can you provide some sample code?

Solution
Checking for free disk space before proceeding with a process is a wise move if disk space is tight or a high percentage of the drive is needed for the process. It is disconcerting to have a process run for hours only to fail towards the end of the process due to insufficient disk space. Although a few different options are available to check for disk space (CLR, WMI, PowerShell, etc.) in SQL Server, let's see how we can use the xp_fixeddrives extended stored procedure which is available in SQL Server 2000 to 2008.

Sample Stored Procedure to Assess the Free Disk Space on a SQL Server Disk Drive

In the sample stored procedure below, it is accepting a parameter for the minimum amount of megabytes (MB) free on a specific disk drive, then executing the master.sys.xp_fixeddrives extended stored procedure into a temporary table. Once the data is in the temporary table the current amount of free disk space is compared to the minimum amount of free disk space to determine if the process should continue or raise an error.

One item to keep in mind is that between SQL Server 2000 and SQL Server 2005/2008 the owner for the xp_fixeddrives extended stored procedure changed. In SQL Server 2000, xp_fixeddrives was owned by dbo and in SQL Server 2005/2008 the owner is sys. Due to this ownership change, two stored procedures are provided below. One for SQL Server 2005/2008 and a second for SQL Server 2000.

*** NOTE *** - SQL Server 2008 and 2005 Version

CREATE PROCEDURE dbo.spExec_SufficientDiskSpace @MinMBFree int, @Drive char(1) AS
/*
----------------------------------------------------------------------------
-- Object Name: dbo.spExec_SufficientDiskSpace
-- Project: Admin Scripts
-- Business Process: Monthly Sales Reports
-- Purpose: Validate sufficient disk space
-- Detailed Description: Validate sufficient disk space based on based on the 
-- @MBfree and @Drive parameters 
-- Database: Admin
-- Dependent Objects: master.sys.xp_fixeddrives
-- Called By: Admin Scripts
-- Upstream Systems: Unknown
-- Downstream Systems: Unknown
-- 
--------------------------------------------------------------------------------------
-- Rev | CMR | Date Modified | Developer | Change Summary
--------------------------------------------------------------------------------------
-- 001 | N\A | 03.05.2009 | MSSQLTips | Original code
--
*/


SET NOCOUNT ON

-- 1 - Declare variables
DECLARE @MBfree int
DECLARE @CMD1 varchar(1000)

-- 2 - Initialize variables
SET @MBfree = 0
SET @CMD1 = ''

-- 3 - Create temp tables
CREATE TABLE #tbl_xp_fixeddrives
(Drive varchar(2) NOT NULL,
[MB free] int NOT NULL)

-- 4 - Populate #tbl_xp_fixeddrives
INSERT INTO #tbl_xp_fixeddrives(Drive, [MB free])
EXEC master.sys.xp_fixeddrives

-- 5 - Initialize the @MBfree value
SELECT @MBfree = [MB free]
FROM #tbl_xp_fixeddrives 
WHERE Drive = @Drive

-- 6 - Determine if sufficient fre space is available
IF @MBfree > @MinMBFree
 BEGIN
  RETURN
 END
ELSE
 BEGIN
  RAISERROR ('*** ERROR *** - Insufficient disk space.', 16, 1)
 END

-- 7 - DROP TABLE #tbl_xp_fixeddrives
DROP TABLE #tbl_xp_fixeddrives

SET NOCOUNT OFF
GO

*** NOTE *** - SQL Server 2000 Version

CREATE PROCEDURE dbo.spExec_SufficientDiskSpace @MinMBFree int, @Drive char(1) AS
/*
----------------------------------------------------------------------------
-- Object Name: dbo.spExec_SufficientDiskSpace
-- Project: Admin Scripts
-- Business Process: Monthly Sales Reports
-- Purpose: Validate sufficient disk space
-- Detailed Description: Validate sufficient disk space based on based on the 
-- @MBfree and @Drive parameters 
-- Database: Admin
-- Dependent Objects: master.sys.xp_fixeddrives
-- Called By: Admin Scripts
-- Upstream Systems: Unknown
-- Downstream Systems: Unknown
-- 
--------------------------------------------------------------------------------------
-- Rev | CMR | Date Modified | Developer | Change Summary
--------------------------------------------------------------------------------------
-- 001 | N\A | 03.05.2009 | MSSQLTips | Original code
--
*/

SET NOCOUNT ON

-- 1 - Declare variables
DECLARE @MBfree int
DECLARE @CMD1 varchar(1000)

-- 2 - Initialize variables
SET @MBfree = 0
SET @CMD1 = ''

-- 3 - Create temp tables
CREATE TABLE #tbl_xp_fixeddrives
(Drive varchar(2) NOT NULL,
[MB free] int NOT NULL)

-- 4 - Populate #tbl_xp_fixeddrives
INSERT INTO #tbl_xp_fixeddrives(Drive, [MB free])
EXEC master.dbo.xp_fixeddrives

-- 5 - Initialize the @MBfree value
SELECT @MBfree = [MB free]
FROM #tbl_xp_fixeddrives 
WHERE Drive = @Drive

-- 6 - Determine if sufficient fre space is available
IF @MBfree > @MinMBFree
 BEGIN
  RETURN
 END
ELSE
 BEGIN
  RAISERROR ('*** ERROR *** - Insufficient disk space.', 16, 1)
 END

-- 7 - DROP TABLE #tbl_xp_fixeddrives
DROP TABLE #tbl_xp_fixeddrives

SET NOCOUNT OFF
GO