Error

[ERROR] VSS_E_INSUFFICIENT_STORAGE

Cause

There is not enough storage available to complete the snapshot.

Resolution

1. Check the free space on all the volumes that have backup sources in the backup configuration. VSS requires a bare minimum of 320MB free space to function properly.
2. Check & increase the amount of storage assigned to shadow copies via either
   1. The vssadmin CLI utility, OR
   2. Via the GUI