How to fix Error 3280 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 3280 – “Backups on raw devices are not supported”

Why This Error Happens

This error occurs when SQL Server’s BACKUP or RESTORE command points to a target path that resolves to a raw disk partition instead of a formatted file system path with a valid file name. Raw devices (unformatted partitions referenced directly, such as \\.\PhysicalDriveX or a bare volume GUID path without a file name) were deprecated in older SQL Server versions and are fully unsupported in SQL Server 2025. This typically happens due to legacy backup scripts, incorrect UNC/volume path syntax, or maintenance plans that were migrated from very old SQL Server instances without updating the destination path format.

Step-by-Step Resolution Guide

Step 1: Identify the Backup Destination Path in the Failing Script

  • Open the SQL Agent Job, maintenance plan, or T-SQL script that triggered the error.
  • Look for the TO DISK = or TO URL = clause in the BACKUP DATABASE statement.
  • Check if the path resembles a raw device reference, e.g., BACKUP DATABASE [MyDB] TO DISK = '\\.\PhysicalDrive2' or a bare drive path like E:\ without a file name.

Step 2: Correct the Path to Use a Valid File System Location

  • Update the destination to a fully qualified file path that includes a drive letter (or mounted volume), folder structure, and file name with a .bak extension.
  • Example corrected syntax:
  BACKUP DATABASE [MyDB] 
  TO DISK = 'E:\SQLBackups\MyDB_Full.bak' 
  WITH INIT, COMPRESSION;
  • If using a mounted volume instead of a drive letter, ensure the mount point is NTFS/ReFS formatted and accessible, e.g., C:\MountPoints\SQLData\MyDB_Full.bak.

Step 3: Verify the Target Volume Is Properly Formatted and Mounted

  • Open Disk Management (diskmgmt.msc) on Windows Server 2025 / Windows 11.
  • Confirm the target disk shows a File System value (NTFS or ReFS) and is not listed as “Unallocated” or “Raw.”
  • If the volume shows as RAW, format it first:
  Format-Volume -DriveLetter E -FileSystem NTFS -Confirm:$false

Step 4: Validate SQL Server Service Account Permissions

  • Ensure the SQL Server service account has Write and Modify NTFS permissions on the target backup folder.
  • Right-click the folder → Properties → Security tab → confirm the SQL Server service account (e.g., NT SERVICE\MSSQLSERVER) is listed with appropriate access.
  • Apply changes and restart the SQL Server service if permissions were modified.

Step 5: Re-run the Backup Job

  • Execute the corrected BACKUP DATABASE statement manually in SQL Server Management Studio (SSMS) to confirm the fix before re-enabling the scheduled job.

Alternative or Verification Steps

  • Run RESTORE VERIFYONLY FROM DISK = 'E:\SQLBackups\MyDB_Full.bak' to confirm the backup file is valid and readable.
  • If the error persists, check for any third-party backup software or SAN snapshot tools that may be exposing raw device paths to SQL Server instead of standard file system paths.