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Fixing “one or more critical volumes is not having enough free space” also known as 0x81000033 during Windows backup

Posted by jpluimers on 2020/02/03

If you get this error:

Backup and Restore failed and you receive the following error message: The backup did not complete successfully. Check your backup: Windows Backup skipped backing up system image because one or more critical volumes is not having enough free space.

then you are dealing with error 0x81000033 which usually means your SYSTEM RESERVED partition is full, but might happen on other volumes you are backing up as well.

Windows tries to trick your mind, as the error actually indicates the disk you make your backup to, but in fact it is about one or more of the disks you are backing up.

Most often, this is the hidden partition SYSTEM RESERVED (sometimes called System Reserved):

The SYSTEM RESERVED partition (~100 megabyte on systems originally installed with Windows < 8 and ~350 megabyte afterwards) contains files relating to boot, recovery and BitLocker drive encryption. You find more information about it here:

The minimum free size for volumes when using Windows backup are these:

  • volumes less than 500 megabytes: 50 megabytes free space
  • between 500 megabytes and 1 gigabytes: 320 megabytes of free space
  • more than 1 gigabytes: at least 1 gigabyte of free space

That was indeed the case on my disk:

Freeing space on the System Reserved volume

A quick search for 0x81000033 reveals space issues usually are about the USN Journal which you can configuring using fsutil.

Even though the documentation doesn’t tell, fsutil accepts not just a drive letter as VolumePath, but also a VolumeName. [WayBack] 1_multipart_xF8FF_3_WolfC07.pdf (Chapter 7 of “Troubleshooting Microsoft Technologies: The Ultimate Administrator’s Repair Manual“) gets that right:

volumepath … specify the path to a logical volume (drive letter, mount path, volume name).

So you do not need a drive letter to disable the USN journal, the volumename suffices.

This volume name is the unique NTFS identification for a volume: [WayBack] NTFS Curiosities (part 2): Volumes, volume names and mount points – Antimail

You can find the volume name inside PowerShell by using Get-Volume | Format-List, then on an administrative command prompt running this:

fsutil usn deletejournal /D \\?\Volume{b41b0670-0000-0000-00e8-0e8004000000}\

In my case this wasn’t enough, so I had to assign a drive letter to see that there was a snapshots directory in the root:

Deleting that directory solved the problem.

Related articles:


Example PowerShell when piping Get-Volume through Format-List for my SYSTEM RESERVED partition via [WayBack] Access to a disk drive using volume ID instead of a drive letter in Windows – Super User:

ObjectId             : {1}\\ACER-M3900\root/Microsoft/Windows/Storage/Providers_v2\WSP_Volume.ObjectId="{5b16a307-de54-11e7-8aeb-806e6f6e6963}:VO:\\?\Volume{b41b0670-0000-0000-00e8-0e8004000000}\"
PassThroughClass     :
PassThroughIds       :
PassThroughNamespace :
PassThroughServer    :
UniqueId             : \\?\Volume{b41b0670-0000-0000-00e8-0e8004000000}\
AllocationUnitSize   : 4096
DedupMode            : NotAvailable
DriveLetter          :
DriveType            : Fixed
FileSystem           : NTFS
FileSystemLabel      : SYSTEM RESERVED
FileSystemType       : NTFS
HealthStatus         : Healthy
OperationalStatus    : OK
Path                 : \\?\Volume{b41b0670-0000-0000-00e8-0e8004000000}\
Size                 : 105058304
SizeRemaining        : 33992704
PSComputerName       :


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