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List of VSS Writers and Services

  • This article is for Windows only

Carbonite Safe Server Backup (CSSB) utilizes a set of built-in Windows functions known as Volume Shadowcopy Services, or VSS. VSS allows backups of in-use, locked, or open files without interrupting whatever process or user is currently accessing those files. This is especially useful for databases, as it allows backups to be performed while the database is active without requiring downtime.

Most backup types in CSSB will rely upon one or more VSS Writers. Each backup type will have its own set of Writers, and each Writer is controlled by a Windows Service. A list of currently-available Writers can be accessed via the command prompt on any Windows computer. Run command prompt as an Administrator and run the command: vssadmin list writers.

This command will list all of the Writers currently available on the machine and display the state of each.

The sections below are collapsed. Please click the section title to open / close a particular section.

VSS Writer States
  • A Writer in the Stable state is ready and waiting to perform a backup. Ideally, all Writers should be Stable when no backups are in progress.
  • Writers in the Failed or Unstable states have encountered a problem, and must be reset to bring the Writer back to a Stable state.
  • Writers that display as In-Progress or Waiting for Completion are currently in use by some backup process. When the backup is finished, the Writer will revert to the Stable state.
    • If a Writer is listed as In-Progress or Waiting for Completion when no backups are running, the Writer may be "stuck". Stuck writers must be reset like a Failed or Unstable Writer.
How to Reset a VSS Writer

In most cases, the Windows Service that controls a VSS Writer can be restarted. This usually brings the Writer back to a stable state. For example, the Microsoft Exchange Writer is controlled by the Microsoft Exchange Information Store (MEIS) service. If the Exchange Writer becomes Unstable, the MEIS service can be restarted to bring the Writer back to the Stable state.

It is important to note that not all services that control VSS Writers can be restarted. If a service cannot be restarted, a reboot of the machine is required. For example, the VSS Writers associated with System State usually require a reboot.

It is also important to note that restarting some services can cause downtime for the application that is related to the service. In our Exchange example above, Exchange would be unable to send or receive email while the MEIS service was offline. Please plan accordingly.

A reference list of VSS Writers and their controlling services can be found below.

List of VSS Writers

The following list shows the VSS Writers used for each backup type and the service that controls these Writers.

Note: This list is for reference use only and is not comprehensive. A system may have active Writers that are not in this list.

Note: For System State, not all Writers in this list are required for the backup to complete. Some Writers will only be present if the corresponding Windows components are installed on the system. For example, the the NTDS Writer will only be present on Domain Controllers with Active Directory installed. This is normal

Backup TypeRequired VSS WriterName of Controlling ServiceService Display Name
System StateASR WriterVSSVolume Shadow Copy
BITS WriterBITSBackground Intelligent Transfer Service
COM+ REGDB WriterVSSVolume Shadow Copy
DFS Replication Service WriterDFSRDFS Replication
IIS Config WriterAppHostSvcApplication Host Helper Service
IIS Metabase WriterIISADMINIIS Admin Service
NTDS Writer[unknown]Active Directory
Registry WriterVSSVolume Shadow Copy
Shadow Copy Optimization WriterVSSVolume Shadow Copy
System WriterCryptSvcCryptographic Services
WMI WriterWinmgmtWindows Management Instrumentation
Microsoft ExchangeMicrosoft Exchange WriterMSExchangeISMicrosoft Exchange Information Store
Hyper-VMicrosoft Hyper-V VSS WriterVMMSHyper-V Virtual Machine Management
Microsoft SQL ServerSQL Server VSS WriterSQL Server VSS WriterSQL Server VSS Writer
SharepointSharepoint VSS WriterSharepoint VSS WriterSharepoint VSS Writer
Sharepoint 2007SPSearch VSS WriterWindows Sharepoint Services SearchSPSearch VSS Writer
Sharepoint 2007OSearch VSS WriterOffice Sharepoint Services SearchOSearch VSS Writer
Sharepoint 2010SPSearch4 VSS WriterSharepoint Foundation Search V4SPSearch 4 VSS Writer
Sharepoint 2010OSearch14 VSS WriterSharepoint Server Search 14OSearch VSS Writer
Sharepoint 2013OSearch15 VSS WriterOSearch15SharePoint Server Search 15
MailStore VSS WriterMailStore VSS WriterMailStore VSS WriterMailStore VSS Writer
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