31418: Acronis Cyber Protect: Backup Fails with "There is not enough space on the volume where the snapshot storage is located"

Last update: 04-10-2021

Increase the storage size or change the storage location of the volume snapshot


Disk/partition or file-level backup fails with the following error:

Not enough space to create a volume snapshot on the volume where the snapshot storage is located.


Not enough space to create a volume snapshot on the volume where the snapshot storage is set.


There is not enough space on the volume where the snapshot storage is located

or error in Windows event log

Event ID:  25
The shadow copies of volume G: were deleted because the shadow copy storage could not grow in time. Consider reducing the IO load on the system or choose a shadow copy storage volume that is not being shadow copied.


There is not enough space for the snapshot storage on the source disk.

Once a snapshot is created during backing up, all the subsequent I/O operations are cached in a temporary storage called snapshot storage. If the amount of I/O operations is too large, the space for caching them can end.

For more information about snapshots see Acronis Cyber Backup Creates a Temporary File During Snapshot


One of the ways to avoid this issue is to perform backups when the I/O load is lower.

You can also free up space on the source disk or move the storage to a volume with more free space (on server operating systems only).

Acronis uses the same drive to create a shadow copy by default if VSS is enabled. Moving VSS Shadow Storage can be useful if you need to:

  • Use a different drive with more free space available to create a snapshot
  • Distribute the snapshot I/O load to a different drive on production devices
  • Perform a successful snapshot of a disk that may be damaged

Acronis Cyber Protect Cloud, Acronis Cyber Protect 15 and Acronis Cyber Backup 12.5

Microsoft VSS provider by default uses the same volume for storing snapshots with the small Maximum Shadow Copy Storage space parameter value.

The vssadmin command line tool should be used to check and configure the VSS storage parameters.

First you will need to list the shadow storages by using the vssadmin list shadowstorage command. See also Microsoft TechNet: Vssadmin list shadowstorage.

In the command line (Start-Run -> cmd), issue the following command:
vssadmin list shadowstorage

You will get the list of associations:

For volume: (C:)\\?\Volume{34e2a3b2-3136-11df-81bf-806e6f6e6963}\
Shadow Copy Storage volume: (C:)\\?\Volume{34e2a3b2-3136-11df-81bf-806e6f6e6963}\
Used Shadow Copy Storage space: 1.815 GB (1%)
Allocated Shadow Copy Storage space: 2.315 GB (1%)
Maximum Shadow Copy Storage space: 2.419 GB (1%)

(!) If no shadow storages are specified, the operating system defines the volume to store snapshots automatically.

On server operating systems you can change the current volume of where the storage is to a different one with the vssadmin delete shadowstorage and vssadmin add shadowstorage commands. This will delete the current shadow storage and create a new one on the volume you specify. See also Microsoft TechNet: Vssadmin delete shadowstorage and Vssadmin add shadowstorage.

Only server operating systems support the Shadow Copy transporting functionality.

For example:
vssadmin delete shadows /for=c:
vssadmin delete shadowstorage /for=c: /on=c:
vssadmin add shadowstorage /for=c: /on=d: /maxsize=20GB

As a result, all snapshot data of volume C: will be cached on volume D:.

You can also increase the maximum amount of storage space that can be used for shadow copy storage using the following command:

vssadmin resize shadowstorage

See Microsoft documentation for more details: vssadmin resize shadowstorage

More information

Troubleshoot VSS-related issues with the free Acronis VSS Doctor tool. If it didn't help, please contact Acronis Support.