VSS: Insufficient Storage.(Async Operation)

Symptoms

The error might be reported during backup (sets configured with VSS).

Cause

There maximum shadow storage space limit is too low.

Workaround

To check the current shadow storage settings (shadow storage associated with a certain volume and its location), from an administrative command prompt run the command:
vssadmin list shadowstorage
For a certain volume (C: in this example), add shadow storage to correct the problem.

vssadmin add shadowstorage /for=c: /on=c: /maxsize=25%