How to detect if the disk space is running low on SQL Server.
There are two different ways to do the same. I personally prefer method 2 as that is very easy to use and I can use it creatively along with database name.
Method 1:
EXEC MASTER..xp_fixeddrives
GO
–Above query will return to us two columns, drive name and MB free. If we want to use this data in our query, we will have to create a temporary table and insert the data from this stored procedure into the temporary table and use it.
 
Method 2:
SELECT DISTINCT dovs.logical_volume_name AS LogicalName,
dovs.volume_mount_point AS Drive,
CONVERT(INT,dovs.available_bytes/1048576.0) AS FreeSpaceInMB
FROM sys.master_files mf
CROSS APPLY sys.dm_os_volume_stats(mf.database_id, mf.FILE_ID) dovs
ORDER BY FreeSpaceInMB ASC
GO
–The above query will give us three columns: drive logical name, drive letter and free space in MB.
We can further modify above query to also include database name in the query as well.
SELECT DISTINCT DB_NAME(dovs.database_id)DBName,
dovs.logical_volume_name AS LogicalName,
dovs.volume_mount_point AS Drive,
CONVERT(INT,dovs.available_bytes/1048576.0) AS FreeSpaceInMB
FROM sys.master_files mf
CROSS APPLY sys.dm_os_volume_stats(mf.database_id, mf.FILE_ID) dovs
ORDER BY FreeSpaceInMB ASC
GO
–The above query will now additionally include the physical file location as well
SELECT DISTINCT DB_NAME(dovs.database_id)DBName,
mf.physical_name PhysicalFileLocation,
dovs.logical_volume_name AS LogicalName,
dovs.volume_mount_point AS Drive,
CONVERT(INT,dovs.available_bytes/1048576.0) AS FreeSpaceInMB
FROM sys.master_files mf
CROSS APPLY sys.dm_os_volume_stats(mf.database_id, mf.FILE_ID) dovs
ORDER BY FreeSpaceInMB ASC
GO
— Individual File Sizes and space available for current database
— (Query 36) (File Sizes and Space)
SELECT f.name AS [File Name] , f.physical_name AS [Physical Name],
CAST((f.size/128.0) AS DECIMAL(15,2)) AS [Total Size in MB],
CAST(f.size/128.0 CAST(FILEPROPERTY(f.name, ‘SpaceUsed’) AS int)/128.0 AS DECIMAL(15,2))
AS [Available Space In MB], [file_id], fg.name AS [Filegroup Name]
FROM sys.database_files AS f WITH (NOLOCK)
LEFT OUTER JOIN sys.data_spaces AS fg WITH (NOLOCK)
ON f.data_space_id = fg.data_space_id OPTION (RECOMPILE);

With T-SQL you can also get the location of the backup, see here Getting the physical device name and backup time for a SQL Server database

SELECT          physical_device_name,
backup_start_date,
backup_finish_date,
backup_size/1024.0 AS BackupSizeKB
FROM msdb.dbo.backupset b
JOIN msdb.dbo.backupmediafamily m ON b.media_set_id = m.media_set_id
-- WHERE database_name = 'YourDB'ORDER BY backup_finish_date DESC
–If the backup wasn’t created in the default location, you can use this T-SQL (run this in SSMS) to find the file path for the most recent backup for all DBs on your SQL Server instance:
SELECT  DatabaseName = x.database_name,
        LastBackupFileName = x.physical_device_name,
        LastBackupDatetime = x.backup_start_date
FROM (  SELECT  bs.database_name,
                bs.backup_start_date,
                bmf.physical_device_name,
                  Ordinal = ROW_NUMBER() OVER( PARTITION BY bs.database_name ORDER BY bs.backup_start_date DESC )
          FROM  msdb.dbo.backupmediafamily bmf
                  JOIN msdb.dbo.backupmediaset bms ON bmf.media_set_id = bms.media_set_id
                  JOIN msdb.dbo.backupset bs ON bms.media_set_id = bs.media_set_id
          WHERE   bs.[type] = ‘D’
                  AND bs.is_copy_only = 0 ) x
WHERE x.Ordinal = 1
GO