eFI partition backup fails with "Error E4F30170: Insufficient storage to complete VSS Shadow Copy."

Problem : 

EFI partition backup fails with "Error E4F30170: Insufficient storage to complete VSS Shadow Copy."

Error Message : 

Error EC8F17B7: Cannot create recovery points for job: Drive Backup of (E:\). Error E4F30170: Insufficient storage to complete VSS Shadow Copy."

Cause :

EFI drive does not have enough free space to create snapshots on it. Windows will then try to route the snapshots to an alternate drive in the same disk and will fail if that drive is an Encrypted/4K drive . 

Solution :

1. Existing snapshots in the EFI partition can be deleted using the command ;

   "vssadmin delete shadows /for={EFI_DRIVE_GUID} /all "

Note: {EFI_DRIVE_GUID} can be found using the "mountvol" command in the command shell. Output will show the list of GUIDs present and the GUID without a drive letter will be the one for EFI partition.

2. Journal entries in the EFI partition can be cleared by assigning it a drive letter and by executing the command

   "FSUTIL USN DELETEJOURNAL /N /D X: " 

where X: is the drive letter assigned to the EFI partition.

3. Differential area for snapshot creation can be resized using the command,

   "vssadmin resize shadowstorage /for={EFI_DRIVE_GUID} /on={EFI_DRIVE_GUID} /maxsize=50%"

If the job still fails with the same error, it is recommended to log a ticket with Microsoft to see if they can assist with increasing space in the EFI drive, to allow snapshots to be created. 

Alternatively a Non Encrypted/512 Bytes/Sector NTFS drive, defined on the same disk, can be used for targeting EFI partition snapshots.