VSS Error, What am i missing

Hi Everyone,

I am new to the software, currently trying to setup backups.

I have installed Duplicacy GUI on a windows server 2012 R2 and I am trying to backup a file share (mapped as network drive) to backblaze.

At first my backup failed because a file was open, I looked it up and the solution is to vss so open files can be backed up.

I then used the -vss option but it failed with error message

ERROR VSS_START Shadow copy creation failed: StartSnapshotSet returned 80042316

In event viewer it shows the following

Volume Shadow Copy Service error: Unexpected error querying for the IVssWriterCallback interface. hr = 0x80070005, Access is denied.
. This is often caused by incorrect security settings in either the writer or requestor process.

Gathering Writer Data

I have already enabled file server VSS agent service on the remote file server. On this backup server I am running everything as Admin account.

what am i missing?

thanks for your input.

Are you trying to backup the network share via the mapped network drive letter? Because that won’t work with VSS. VSS has to run on the filesystem hosting the files.

Why don’t you run Duplicacy directly on the file server?

Also, while you may be using the Admin account, you still have to run Duplicacy with elevated privileges (Run as administrator).


I have run it as Administrator, the reason i prefer to run it on a separate machine is to avoid stress on the file server.

i have seen other backup software take snapshots from remote file servers / shares and looking at MS documentation they have the ability


just reading through it now.

Hi @rsp, welcome to the forum!
Generally I do agree with @Droolio, much easier to run it locally on the server (and simple is often more robust) but this might be interesting for enterprise users.
I don’t think Duplicacy natively supports VSS for SMB File Shares (at least not yet).
(The built-in (2012) Windows backup apparently doesn’t do this either)

You probably found this technet article too whicih is older but have more information:

I haven’t tried this but a quick read indicates to me:

  • The remote file server needs the File Server VSS Agent Service.
  • Your Backup machine needs the File Share Shadow Copy Provider (installed by default on Windows Server, but not on non-server Windows so you might need to add this)
  • The account used to run the backup needs to be member of Backup Operators of the remote server. (as for general backup)

So it looks like it could be possible to

  • use diskshadow.exe to prepare VSS for the backup
  • Perform a backup with :d:
  • use diskshadow.exe to delete the VSS copy

Let us know how it works for you!
Make sure you plan for and test restores as well!