Windows Server Backup Stuck on Reading Data? Fixes

If Windows Server Backup is stuck on “Reading data” during a backup or restore, the process has usually hung because of a problematic volume, a corrupted catalog, or a stalled VSS (Volume Shadow Copy) service. Restarting the backup service and the VSS service, then re-running the backup, resolves the issue in most cases. Below are the detailed steps and background to get the backup moving again.

Why “Reading data” Gets Stuck

Windows Server Backup (WSB) reads the source volumes through the Volume Shadow Copy Service (VSS) to create a consistent snapshot. The “Reading data” phase appears after the snapshot is created and while the backup engine copies the data from the snapshot to the destination. If VSS fails to finalize the snapshot, or if the backup engine is waiting on a locked file or a failing disk, the progress bar can stay at 0% or a fixed percentage for hours.

Common triggers include:

• Another backup job (Windows or third-party) running at the same time, causing a VSS conflict.
• Corrupted VSS metadata or a non-functional VSS writer (e.g., Exchange, SQL Server, or Hyper-V writer).
• A volume with file system errors that the backup engine cannot read cleanly.
• Insufficient space on the backup destination, so the copy operation cannot proceed.
• Antivirus software scanning the backup destination or the source files, locking them temporarily.

Step-by-Step Fixes to Try

1. Check the backup destination space. Ensure the destination drive has at least as much free space as the total size of the source volumes being backed up. If it is full, the backup will hang.
2. Stop and restart the services. Open an elevated Command Prompt and run the following commands, one by one:
   net stop swprv
net stop vss
net start vss
net start swprv
   Then restart the Windows Server Backup service with net stop wsbexchange and net start wsbexchange (the service name may vary by version).
3. Run a file system check. Open an elevated Command Prompt and run chkdsk /f on each source volume. You will need to schedule the check for the next reboot if the volume is in use.
4. Clear the backup catalog. If the backup catalog is corrupted, the backup may hang. In an elevated Command Prompt, run wbadmin delete catalog and confirm. This removes the catalog of previous backups but does not delete the backup files themselves. You can then re-run the backup.
5. Disable third-party antivirus temporarily. If the hang is caused by antivirus locking files, temporarily disable real-time protection and try the backup again. Re-enable it after the test.
6. Reboot the server. A clean restart clears any stuck processes and releases file locks. After reboot, run the backup again.

How to Prevent the Hang in Future

To reduce the chance of a repeat, follow these practices:

• Schedule backups at a time when no other VSS-using tasks (like Exchange or SQL maintenance) are running.
• Keep the backup destination on a separate physical disk, not the same disk as the source volumes.
• Monitor the backup destination space and set up alerts for low free space.
• Regularly run chkdsk on all volumes to catch file system errors early.
• If you use a third-party backup tool, ensure it is compatible with Windows Server Backup and VSS.

When to Use wbadmin Instead of the GUI

The Windows Server Backup GUI can sometimes hide the exact error. Using the command-line wbadmin tool gives clearer output. For example, to start a backup of the C: drive to the E: drive, run:

wbadmin start backup -backupTarget:E: -include:C: -quiet

If the backup hangs, the command will show the last action and may produce an error code. You can also check the event logs for VSS and Backup events under Event Viewer > Applications and Services Logs > Microsoft > Windows > Backup.

Common Misconception: “Reading data” Means the Backup Is Copying Slowly

Many admins think a stuck “Reading data” is just a slow copy. In reality, the copy phase is usually fast for moderate amounts of data. If the progress bar does not move for more than 30 minutes, it is likely hung, not slow. Check the disk activity on the destination drive: if the activity light is idle, the backup is stuck.

Alternatives to Windows Server Backup

If Windows Server Backup continues to hang, consider using a different backup solution. Built-in options like wbadmin with a different destination (network share, external drive) can help. Third-party tools (e.g., Veeam, Acronis) have their own VSS handling and may be more reliable for complex workloads like Hyper-V or SQL. However, for a simple file server, Windows Server Backup is usually sufficient once the hang is resolved.

Frequently Asked Questions

How long should “Reading data” normally take?

It depends on the volume size and disk speed. A typical backup of 100 GB to a USB 3.0 drive might take 10-20 minutes. If it exceeds an hour with no progress, it is stuck.

Will deleting the backup catalog delete my backups?

No. The catalog is just a metadata index. Deleting it makes the existing backups invisible to Windows Server Backup, but the files remain on the destination. You can re-import them later with wbadmin recover if needed.

Can I run a backup while another backup is running?

No. Windows Server Backup does not support concurrent backups. Running two jobs simultaneously will cause one to hang. Always wait for the first to finish.

Does the backup hang if a file is locked by an application?

VSS is designed to handle locked files by creating a snapshot. However, if the VSS writer for that application is faulty, the snapshot may not be created, and the backup can hang. Check the VSS writer status with vssadmin list writers.

What if the server is a domain controller?

Backing up a domain controller requires the System State to be included. If the backup hangs, ensure the AD DS VSS writer is healthy. You may need to run ntdsutil to do a metadata cleanup if the writer is stuck.

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