VSS is used to backup MS Exchange, MS SQL, System State, MS Sharepoint, & Hyper-V data. VSS is a Microsoft product that is included in Windows. As such there is a slight different approach to errors relating to it.
There are a number of errors that can be presented by the Redstor client, these are pulled from the Windows VSS services and can also be seen in the Windows application event logs.
The first place to start with VSS errors is to run the command line “vssadmin list writers”. Depending on the Windows roles & products installed, it will vary the number of writers you have. In a healthy system though you should find all report as ‘ Stable’ with ‘No error’ as seen below.
If any of the writers report as anything other than  Stable then you will need to try and reload the VSS writers to get them stable.
The first step is to restart the VSS service, many VSS writers will run under the "VSS" service. Below is a list of the services you may need to restart depending on which VSS writer is failed.
|VSS Writer||Process (.exe)||Service|
|ASR Writer||VSS||Volume Shadow Copy|
|BITS Writer||BITS||Background Intelligent Transfer Service|
|COM+ REGDB Writer||VSS||Volume Shadow Copy|
|DFS Replication Service Writer||DFSR||DFS Replication|
|DHCP Jet Writer||DHCPServer||DHCP Server|
|FRS Writer||NtFrs||File Replication|
|FRSM Writer||srmsvc||File Server Resource Manager|
|IIS Config Writer||AppHostSvc||Application Host Helper Service|
|IIS Metabase Writer||IISADMIN||IIS Admin Service|
|Microsoft Exchange Replica Writer||MSExchangeRepl||Microsoft Exchange Replication Service|
|Microsoft Exchange Writer||MSExchangeIS||Microsoft Exchange Information Store|
|Microsoft Hyper-V VSS Writer||vmms||Hyper-V Virtual Machine Management|
|MSMQ Writer||MSMQ||Message Queuing|
|MSSearch Service Writer||WSearch||Windows Search|
|NTDS||NTDS||Active Directory Domain Services|
|O_Search VSS Writer||OSearch||Office SharePoint Server Search|
|O_Search 14 VSS Writer||OSearch14||SharePoint Server Search 14|
|Registry Writer||VSS||Volume Shadow Copy|
|Shadow Copy Optimization Writer||VSS||Volume Shadow Copy|
|SPSearch VSS Writer||SPSearch||Windows SharePoint Services Search|
|SPSearch4 VSS Writer||SPSearch4||SharePoint Foundation Search V4|
|SqlServerWriter||SQLWriter||SQL Server VSS Writer|
|System Writer||CryptSvc||Cryptographic Services|
|TermServLicensing||TermServLicensing||Remote Desktop Licensing|
|WIDWriter||WIDWriter||Windows Internal Database VSS Writer|
|WINS Jet Writer||WINS||Windows Internet Name Service (WINS)|
|WMI Writer||Winmgmt||Windows Management Instrumentation|
After restarting the service please run the vssadmin command again to check whether the writer is still in a failed state. If there is no improvement a full reboot of the server may be required.
If neither of these have fixed the issue, please check the event logs around the time of the error/backup and check the VSS service for errors. Please check these against the Microsoft Technet pages.
If you need any assistance, please create a ticket with:
- Windows Application and System Event Logs in .evtx format
- Device Name
- The output file of the following commands:
- vssadmin list writers >C:\writers.txt
- vssadmin list providers >C:\providers.txt
- vssadmin list shadows >C:\shadows.txt
- vssadmin list shadowstorage >C:\shadowstorage.txt
- The amount of disks that you have, plus the free disk space on each