Overview of VSS system writer waiting for completion
The Shadow Copy Service(VSS) System Writer is used by the cryptographic services provided by the operating system. It is used to enumerate and replace system files when the signature of a system file is different from the signature stored in the security catalog database.
Sometimes, when you perform a backup on Windows Server based computer that uses the VSS system writer, the backup fails. If you check VSS writer on exchange Server, the Microsoft exchange write shows waiting for completion.
While investigating the VSS backup failure issue we observed that VSS backup fails when the VSS is in waiting for completion state. VSS backups are successful on those systems where system writer is in stable state. From a command line one can see the status of the Volume Shadow Copy writers by typing vssadmin list writers. A number of the writers will show: State:  Waiting for completion. When you encounter VSS system writer waiting for completion error, you can try the following methods to solve it.
Method 1. Restart Cryptographic Services
Step 1. Type services.msc in the Search Box and press Enter
Step 2. Locate Cryptographic Services observe its current status and open to make changes.
Step 3. From General tab you can Start/Stop and change the Startup type of Cryptographic Services. You should first disable it and save the change. Then locate to the General tab again and select the Startup type as Automatic. At last click OK to save the change.
To finish press OK button and close Services window. Then Run "vssadmin list
writers" and check again.
Method 2. Perform CHKDSK
The disk corruption may also cause VSS waiting for completion error on Windows Server 2003/2008/2012/2016. Therefore, you can run CHKDSK to check disk error.
Step 1. Open the command prompt as administrator.
Step 2. In command prompt type chkdsk c: /r and hit Enter. This assumes Windows is installed on your C: drive. If the drive letter for your system partition is different, type the real one. (You can run diskpart > list volume to check.)
Step 3. Restart the Server and check the VSS state again.
Method 3. Solve VSS waiting for completion with an easier way
As you know, Windows should rely on Volume Shadow Copy Service to create backup. Once you get Volume Shadow Copy Service error, the backup will fail. And you may meet error like VSS waiting for completion or the system writer is not found in the backup. Fortunately, here is a backup tool embedded with built-in VSS technology which allows you to create backup copy even there is something wrong with the Volume Shadow Copy Service - it is AOMEI Backupper.
AOMEI Backupper Server is professional backup and restore software which is designed for Windows 7, Windows 8, Windows 10, Windows XP and Windows Visa. It is easy to use, and you can handle it fast even you are not an expert. It supports to backup system, disk, partition, files and folders. Take system backup as an example. Let’s see how to create VSS backup with AOMEI Backupper.
Step 1. Download AOMEI Backupper and launch the software. Click System Backup under the Backup tab.
Step 2. Select another location as the destination path. (You do not need to choose the source, it will choose automatically.)
Step 3. Click Options, the select VSS. There are two options: Use VSS (Microsoft) and Use AOMEI’s built-in technology.
If the VSS has problems, you can choose to use AOMEI’s built-in technology in order to backup without interrupting and restarting the computer.
Step 4. After all this done, click Start Backup.
With AOMEI Backupper, you will not worry about the error VSS waiting for completion. Even if the VSS system writer missing, you can still protect your computer by creating an image backup via AOMEI Backupper. You can also make a bootable media with this software. If you cannot boot into Windows, you can boot from the bootable device and restore your Server computer to the earlier state.
If you want to protect unlimited PCs and servers within your company, you may choose AOMEI Backupper Technician Plus. It offers unlimited billable technical services to clients. It also enables you to copy installation directory for portable version creation.