Загляните в sys.dm_os_volume_stats()
Пример
Select Distinct
ServerName = @@SERVERNAME
,LogicalDrive = sds.logical_volume_name
,Drive = sds.volume_mount_point
,TotalSpace = sds.total_bytes/1048576
,SpaceAvail = sds.available_bytes/1048576
From sys.master_files sms
Cross Apply sys.dm_os_volume_stats(sms.database_id, sms.FILE_ID) sds
Order By SpaceAvail asc
Возвращает
ServerName LogicalDrive Drive TotalSpace SpaceAvail
JOHNCAPPELLETTI\MSSQLSERVER02 TI106398W0F C:\ 698658 366114