This error is usually caused by insufficient disk space on one volume in the Windows OS being backed up. This can include the System Reserved Partition.
It can also be caused by defining shadow storage associations with a maximum size smaller than necessary to create the shadow copy.
This issue may also occur if the volume is larger than the size which Microsoft VSS supports (64TB).
Operation: [Shadow copies commit]. Code: [0x80042306]
Within the VM guest OS that cannot be backed up or replicated, use the Disk Management utility (diskmgmt.msc) to view free space on each NTFS volume:
If a volume is low on disk space, the solution is to delete files, expand the volume, or redirect shadow copies to another volume. For virtual machines, the simplest solution is usually to increase the size of the VM’s hard disk, then expand the volume in Disk Management.
Although it is sometimes possible to create a shadow copy using less than 1% of the free space on a volume, 15%-20% free space is often required on busy volumes. The smallest amount of space that can be allocated is configurable, but Microsoft Support has recommended maintaining at least 42 MB free on the system reserved partition.
If it is not clear which volume has insufficient space, see “How to Check Which Volume is Causing the Error”, below.
It is possible to change the shadow storage association to use a volume with sufficient free space; The location can be changed from the Shadow Copies utility, or from the command line. To access the utility, right click any volume and choose Configure Shadow Copies.
Warning: This is not recommended in a Hyper-V environment.
To access the utility, right click any volume and choose Configure Shadow Copies. On older server operating systems, this may instead be a tab in Properties.
All commands below should be run from an administrator command prompt.
Use vssadmin list shadowstorage to view existing shadow storage associations. If no shadow storage exists for any volume, the command response will be “No items found that satisfy the query.”
If no association is listed for the volume, run vssadmin add shadowstorage to change the location of the shadow storage area. For example, to redirect shadows from D: to E:
vssadmin add shadowstorage /for=D: /on=E: /maxsize=200GB
If a shadow storage association already exists, run vssadmin resize shadowstorage to change the size of the shadow storage area. For example, to redirect shadows from D: to E:
vssadmin resize shadowstorage /for=D: /on=E: /maxsize=200GB
The /maxsize parameter is not optional, but can be set as /maxsize=UNBOUNDED. Otherwise, a value of 15-20% of the source volume’s size is generally recommended for busy servers.
In some cases, it may not be obvious which volume needs to be modified. To isolate the problem, perform the following steps within the VM guest OS that cannot be backed up or replicated.
Create and then delete a shadow copy of each volume, one at a time. To access the GUI, right click any volume and choose Configure Shadow Copies. On older operating systems, this may instead be a tab in Properties. In the Shadow Copies utility:
This can also be performed using the Diskshadow utility, which may provide a better match for the behavior of the VSS API used by Veeam Backup & Replication.
If the affected volume has sufficient free disk space, the shadow storage limit may be too small. Redirect the shadow copies as shown above, or increase the shadow storage limit.