By Delia / Last update December 13, 2021

The Symptom

Generally, Windows Server Backup (WSB) has Automatic Disk Usage Management feature to delete the oldest backup by default. However, you may still encounter WSB failed with the following error:

“Windows Backup encountered an error while writing to the backup target. Detailed Error: There is not enough space on the disk”

The Cause

WSB saves snapshots in the diff area. The Automatic Disk Usage Management, which is enabled in WSB by default, will shrink the diff area and remove the corresponding backup file to free up space for the next backup. However, WSB will not shrink the diff area to less than 1/8 of target volume size in case of losing all the previous backups. This is why Windows Server Backup failed with not enough space on disk.

Solutions to Server Backup Not Enough Space on the Disk

If you happen to receive this Windows Server backup failed not enough space on disk error, you have three options to get this resolved.

>> Solution 1. Use another larger hard drive as the backup disk.

>> Solution 2. Exclude some items that you are backing up.

>> Solution 3. Manually delete some old snapshots to free up space.

The first two are easy to follow, but you may not want to. So how to remove snapshots? If you are using Windows Server 2012(R2) or Windows Server 2016, you can use wbadmin delete backup command to remove old backups. There are three ways to determine which backup(s) to delete and the parameters are: -keepVersions, -version, or –deleteOldest. For example, to delete all backups except one that was created at 06:48 11/10/2015, use the following command:

Wbadmin delete backup -keepVersion:11/10/2015-06:48 -BackupTarget:F:

In Windows Server 2008/2008 R2, WBadmin only provides commands that allow you to delete system state backup. Usually it is non-system state backups that take up the space because system state backups take less space. To delete snapshots, you need to use diskshadow.exe. You can run the following command from the standard command prompt.

  • diskshadow
  • list shadows all
  • delete shadows id => To delete a shadow copy of the specific ID

or delete shadows all => To delete all the listed shadows.

or delete shadows oldest => To delete the oldest shadow on a target volume.

Choose the proper way to remove snapshots or backups to free up more space. After that, you should have enough space to create backups. The next time backup disk is full, you can repeat these operations to free up more space on the backup disk. If you want to save this trouble of removing backups manually forever, you can use another backup program.

Long-term Solution | Use Windows Server Backup Alternative

If you are not content with the performance of WSB, you can try dedicated Windows Server backup software, AOMEI Backupper Server. Its Disk Space Management can help delete the previous backups no matter how many versions of backup you have created. You will never meet the Server backup not enough space on the disk error.

In addition, compared to WSB can only set one daily backup schedule, it allows you to create multiple daily/weekly/monthly backup schedules to protect your system, important files, disk or partition. Besides full backups, you can also create incremental/differential backups.

Tutorial to set scheduled backup task:

1. Download and run this Windows Server Backup alternative software.

Download Free Trial Win 10/8.1/8/7 & Server
Secure Download

2. Under “Backup” tab, select “System Backup”. You can also select other three backup types based on your needs.

System Backup

3. Click to select a target location to receive the image backups as the needed partition(s) will be included automatically.

Select Path

4. To configure a schedule backup running automatically, click the “Schedule” button down the left bottom. Click "Scheme" to enable Disk Space Management to delete old backup images.

5. Click “Start Backup” to save and run this backup.

Start Backup


  • A system backup or disk backup created with AOMEI Backupper can be restored to dissimilar hardware computer besides the original computer.
  • To protect unlimited PCs and servers within your company, you may choose AOMEI Backupper Technician Plus. It offers unlimited billable technical services to clients. It also enables you to copy installation directory for portable version creation.

How It Works to Avoid Server Backup No Enough Space on the Disk

To make it clear to create a schedule backup task and set up the retention policy for your Windows server backups to prevent no enough space on the disk, refer to the following instructions:

For automatically running a scheduled backup task, select the one of the following options:

  • Daily/Weekly/Monthly: Once setting up, the backup task will running at a specific time, or daily, weekly, monthly to avoid backing up the same content manually.

  • Event Triggers: You could trigger the backup event by the following events: User logon, User logoff, System startup, System shutdown.

  • USB plug in: Once detecting the source or destination USB device of the task is plugged in, AOMEI Backupper will automatically back up the data on the USB or backup data to USB drive.

Schedule Settings

To help you enable Disk Space Management to delete old backup images while exceeding the specified value, refer to this:

Click Scheme -> Enable Backup Scheme, choose a backup scheme and specify the value of backups to retain.

There are 5 schemes to help you to delete old backup image to free up space: Full Backup Scheme, Incremental Backup Scheme, Differential Backup Scheme, Space Management Scheme, Other Backup Scheme.

Backup Scheme

To know more details about how the scheme works, please find more details about backup scheme.


Now you know why you meet the Windows Server backup not enough space on the disk error and the solutions to figure it out. However, as long as you continue using WSB to backup your server, you may also meet the low disk space error sooner or later.

If you want to avoid this problem altogether, you can try another backup tool - AOMEI Backupper Server. Its Disk Space Management feature would automatically delete old backups to free up space. What’s more, it offers more useful functions compared to WSB, such as multiple backup schedules. Go for it now and discover more!