Sql-server – Back Up – Free Drive Space

Alternative could be to use PowerShell to grab the information. All you need is a few commands tied together:

$measure = Get-WmiObject Win32_LogicalDisk | Where {$_.DriveType -eq 5}
if ($measure.FreeSpace -lt 20 { "More logic"} else {"something else"}

You could add in the logic to measure for your limit (value is in bytes). Then use Send-MailMessage cmdlet to actually send out your message. Wrap all that up and then have a SQL Agent job call the script on a scheduled basis.

This can be done through PowerShell. See the below:

Get-PSDrive |
    Where-Object {$_.Provider -like "*FileSystem"} |
    Select-Object Name, Used, Free, @{Name = "Used_Percent"; expression = {$_.Used / ($_.Used + $_.Free) * 100}}

Or, through WMI:

Get-WmiObject -Class Win32_LogicalDisk |
    Select-Object DeviceID, VolumeName, @{Name = "Used_Percent"; expression = {($_.Size - $_.FreeSpace) / $_.Size * 100}}

Please see Aaron's comment to your question. I completely agree with him, this is not something that is easily done through SQL Server. You can finagle this to be run within SQL Server, but it's not necessarily a native way to get this information directly from SQL Server.