Hyper-V backup using Windows Server 2016 Backup

Windows Server Backup SummaryRecovery Option ScreenHi,
 
I am backup Hyper-V server using Windows Server Backup. The size of the backup is about 1,600GB (C drive for OS, E drive for VMs files) and external USB hard drive  size is 3,725GB.
It ran the backup for three days and it only used up so far 1,594GB.
As I understand it, Windows Server Backup program does not do "incremental" backup on virtual machines; therefore it has to do a full backup each and every time. I noticed that it literally took 9-11 hours to complete the backup in the past 3 days. Very slow considering that the server has USB 3.0 ports and USB hard drive is also 3.0.

However if it has to do "complete" backup (because it can't perform incremental backup), then why do I see > 2,100GB space still available on external backup drive after 3 days of backup?
Does it overwrite previous backup? if that is the case, then I can only go back to previous day to restore?
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sgleeAsked:
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MaheshArchitectCommented:
For Full backups, there is setting available in backup tool console named "Performance setting"

There check if you have selected incremental backup option
sgleeAuthor Commented:
Backup Performance OptionIs this what you are referring to?
What do I need to do there?
MaheshArchitectCommented:
if this is not set to incremental, all backup should be full, backup tool deletes old backup if disk space is short

check how many backups you left with by running command

wbadmin get versions
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sgleeAuthor Commented:
icrosoft Windows [Version 10.0.14393]
(c) 2016 Microsoft Corporation. All rights reserved.

C:\Windows\system32>wbadmin get versions
wbadmin 1.0 - Backup command-line tool
(C) Copyright 2013 Microsoft Corporation. All rights reserved.

Backup time: 12/16/2018 8:00 PM
Backup target: 1394/USB Disk labeled \\?\Volume{1b96f4f7-b4b2-4c96-91c3-f8f7fcfc03aa}
Version identifier: 12/17/2018-01:00
Can recover: Volume(s), File(s), Application(s), Bare Metal Recovery, System State
Snapshot ID: {f02da393-a029-4675-a5fe-e1ecfd94b6cf}

Backup time: 12/18/2018 1:00 AM
Backup target: 1394/USB Disk labeled \\?\Volume{1b96f4f7-b4b2-4c96-91c3-f8f7fcfc03aa}
Version identifier: 12/18/2018-06:00
Can recover: Volume(s), File(s), Application(s), Bare Metal Recovery, System State
Snapshot ID: {b466a8de-7f7e-4bbf-8fd9-5f704e659e56}

Backup time: 12/18/2018 11:00 PM
Backup target: 1394/USB Disk labeled \\?\Volume{1b96f4f7-b4b2-4c96-91c3-f8f7fcfc03aa}
Version identifier: 12/19/2018-04:00
Can recover: Volume(s), File(s), Application(s), Bare Metal Recovery, System State
Snapshot ID: {12fc0175-707d-4594-bcef-f720e3f643c2}
Lee W, MVPTechnology and Business Process AdvisorCommented:
I would strongly suggest you look into third party backup products for your VMs.  Altaro (my favorite) and Veeam are two that offer FREE versions to backup your VMs.
sgleeAuthor Commented:
@Lee
I do run NAKIVO backup and it runs well.
I just wanted to understand more about how Windows Server backup runs.
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Windows Server 2016

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