37472: Acronis Cyber Protect Cloud, Acronis Cyber Backup: backup fails with 'The shadow copy provider had an unexpected error while trying to process the specified operation'
Insufficient space allocated for shadow copy or shadow storage not set.
Solution
In order to check that the volume has enough space for the shadow copy, create a shadow copy using the tools integrated in Windows and make sure the shadow copy is created successfully. If required, move the shadow storage to another volume or free up space on the volume.
Go to My Computer -> Right click on any of internal volumes listed -> Configure Shadow Copies
Select the volume you want to check and click on Create shadow copy to confirm that there is sufficient free space on each volume. Otherwise set up the storage area for the volume.
You can also use the vssadmin utility to run this check and create,increase or relocate the shadow storage.
Go to Start -> Run -> diskmgmt.msc. Controll the size of all volumes. If any volume of size 1024 MB or less is present on the disks, it will not be backed up via VSS, see this MSDN article for technical reference. Increase the size of such volume up to 1025 MB and more or exclude it from the backup source.
Go to Control Panel -> System - >System protection
Select the volume you want to check and click on Create shadow copy to confirm that there is sufficient free space on each volume. Otherwise configure protection for the volume and increase the size of the storage.
To check that the volume has enough free space and force the shadow copy creation, run the ntbackup utility and backup some data from the volume you want to check, checking the shadow copy creation. Run cmd and enter ntbackup.exe.
In case you have to create or increase the size of the storage, go to Control Panel -> System -> System restore and configure space for the storage.
If the volume that you back up has enough free space to store the snapshots, you can resize the shadow storage with the vssadmin resize shadowstorage command. See also Microsoft TechNet: Vssadmin resize shadowstorage.
For example: vssadmin resize shadowstorage /for=c: /on=c: /maxsize=20GB
(!) If you would like to allocate all of the volume's free space for the storage, use the unbounded value. E.g. vssadmin resize shadowstorage /for=c: /on=c: /maxsize=unbounded