Microsoft VSS

Microsoft Shadow Copy Provider’s Volume Shadow Copy Service, or simply VSS is the first process of most image based backup solutions.  VSS was first made available for the Windows 2000 Operating System, and has been bundled with every new Operating System since Windows XP.  It is used to create volume shadow copies of a machine that is actively in use.

Between the various versions of Windows as well as versions of applications with VSS support, there are many different VSS Writers each with their own unique function.

To list the VSS writers of any Windows OS simply open up a command prompt and enter in the command:

vssadmin list writers

The result will look similar to what is displayed below:

Microsoft Windows [Version 6.1.7601]

Copyright (c) 2009 Microsoft Corporation. All rights reserved.

C:\Windows\system32>vssadmin list writers

vssadmin 1.1 – Volume Shadow Copy Service administrative command-line tool

(C) Copyright 2001-2005 Microsoft Corp.

Writer name: ‘System Writer’

Writer Id: {e8132975-6f93-4464-a53e-1050253ae220}

Writer Instance Id: {767c1764-6013-42ad-86f0-cdc94ba7bca2}

State: [5] Waiting for completion

Last error: No error

Writer name: ‘ASR Writer’

Writer Id: {be000cbe-11fe-4426-9c58-531aa6355fc4}

Writer Instance Id: {444e1aca-b439-46ac-81e2-4702fb1b478c}

State: [1] Stable

Last error: No error

Writer name: ‘Registry Writer’

Writer Id: {afbab4a2-367d-4d15-a586-71dbb18f8485}

Writer Instance Id: {8e480c8f-edab-4e52-80a4-f9c42a92fd91}

State: [1] Stable

Last error: No error

Writer name: ‘COM+ REGDB Writer’

Writer Id: {542da469-d3e1-473c-9f4f-7847f01fc64f}

Writer Instance Id: {58303128-81b8-4df4-bfa9-3381561b85f1}

State: [1] Stable

Last error: No error

Writer name: ‘BITS Writer’

Writer Id: {4969d978-be47-48b0-b100-f328f07ac1e0}

Writer Instance Id: {104fab54-11d7-4f75-b46f-b18dc818ac93}

State: [1] Stable

Last error: No error

Writer name: ‘WMI Writer’

Writer Id: {a6ad56c2-b509-4e6c-bb19-49d8f43532f0}

Writer Instance Id: {10af4ff1-92b3-4255-bbf1-351eb8ae9fcf}

State: [1] Stable

Last error: No error

This particular output displays the names of 6 separate VSS Writers.  More importantly for troubleshooting purposes this command also displays each of these VSS Writer’s current State as well as their Last error.

Writer name: ‘System Writer’

Writer Id: {e8132975-6f93-4464-a53e-1050253ae220}

Writer Instance Id: {767c1764-6013-42ad-86f0-cdc94ba7bca2}

State: [5] Waiting for completion

Last error: No error

It is possible that nothing will display at all for this command however this is easily resolved by re-registering the VSS DLL Binaries which does not require a reboot.

State of VSS Writers

VSS Writers have several states which directly reflect the current status of each VSS Writer.

Stable

Unknown

Frozen

Failed during freeze operation

Failed

List of Common Writers

Active Directory Domain Services VSS Writer (NTDS)Beginning with Windows Server 2003, this writer reports the NTDS database file (ntds.dit) and the associated log files.  These files are required to restore the Active Directory correctly.

ADAM (instanceN) Writer

Beginning with Server 2003, this writer reports the ADAM database file (adamntds.dit) and the associated log files for each instance in %program files%\Microsoft ADAM\instanceN\data, where N is the ADAM instance number.

These database log files are required to restore ADAM instances.

ADAM (VMwareVCMSDS) Writer

VMWare Virtual Center Server Service for the ADAM instance VMWareVCMSDS

ASR Writer

Automated System Recovery which stores the BCD configuration of disks on the system on OSes starting with Vista and Server 2008.

BITS Writer

Background Intelligent Transfer Service Writer first available in Vista and Server 2008.  BITS uses the FilesNotToBackup registry key to exclude files from the BITS cache folder. The default cache location is %AllUsersProfile%\Microsoft\Network\Downloader\Cache

Certificate Authority

This writer is responsible for enumerating the data files for the Certificate Server

COM+ REGDB Writer

COM+ Class Registration Database Writer responsible for the contents of the %SystemRoot%\Registration directory which was first available in Vista and Server 2008 OSes.

DFS Replication Service Writer

Starting in Server 2003 R2 this writer protects Distributed File System Replication selections data.

DHCP Jet Writer

Starting with Server 2003 this writer is responsible for enumerating files required for the DHCP server roleThis writer is not available for workstation OSes.

Exchange Writer

The Exchange Writer provides the application aware backups for Microsoft Exchange Servers.  It also provides the ability for performing log truncation of Microsoft Exchange Transaction Logs.

Event Log Writer

Responsible for protecting the Event Log Viewer contents.

FRS Writer

Responsible for the File Replication Service starting with Server 2003.

FSRM Writer

Starting with Windows Server 2003 R2, this writer enumerates the FSRM configuration files that are used for system state backup.  During restore operations it prevents changes in FSRM configuration and temporarily halts enforcement of quotas and file screens.  This writer is not available for workstation OSes.

IIS Config Writer

Protects the configuration data for Internet Information Services (IIS).

IIS Metabase Writer

Responsible for the Microsoft Internet Information Services which is required by some SQL Server features.

Microsoft Exchange Writer

Responsible for backing up the Exchange Information Store as well as providing the ability to truncate Exchange transaction logs.

Microsoft Hyper-V VSS Writer

Responsible for backing up Hyper-V Virtual Machines.

MSSearch Service Writer

Starting with Server 2008 this writer exists to delete search index files from shadow copies after creation.  This is done to minimize the impact of Copy-on-Write I/O during regular I/O on these files on the shadow-copied volume.

MSDEWriter

Beginning with Windows Server 2008, this writer exists to delete search index files from shadow copies after creation.  This is done to minimize the impact of Copy-on-Write I/O during regular I/O on these files on the shadow-copied volume.  This Writer is frequently called on by operations from the SQLSERVERAGENT service.

NPS Writer

Responsible for protecting the Network Policy Server.

NPS VSS Writer

Responsible for protecting the Network Policy Server.

Search VSS Writer

Responsible for Search Operations.

Performance Counters Writer

Starting with Windows 7 and Server 2008r2, this writer reports the performance counter configuration files.  These files are only modified during application installation and should be backed up and restored during system state backups and restores.

Registry Writer

The registry writer is responsible for the Windows registry.

SCVMM Express Writer

Responsible for the Microsoft System Center Virtual Machine Manager.

Shadow Copy Optimization Writer

Beginning with Windows Vista and Windows Server 2008, this writer deletes certain files from volume shadow copies.

SMS Writer

Responsible for the System Center Configuration Manager.

SPSearch VSS Writer

Responsible for the SharePoint Server Search operation.

SQL Server Writer

The SQL Server Writer provides the application aware backups for Microsoft SQL Servers.  It also provides the ability for performing log truncation of Microsoft SQL Transaction Logs.

System Writer

Beginning with Windows Vista and Windows Server 2008, the system writer enumerates all operating system and driver binaries.

Task Scheduler Writer

Starting with Windows 7 and Server 2008r2, this writer reports the Task Scheduler’s task files.

TermServLicensing

Responsible for protecting the Microsoft Terminal Server Licensing.

VSS Metadata Store Writer

Starting with Windows 7 and Server 2008r2, This writer reports the writer metadata files for all VSS express writers.

WDS VSS Writer

Beginning with Windows Vista and Windows Server 2008, this writer reports the writer metadata files for all VSS express writers.

WINS Jet Writer

Beginning with Windows Server 2003, this writer is responsible for enumerating files required for WINS.

WMI Writer

Beginning with Windows Vista and Windows Server 2008, this writer is used for identifying WMI-specific state and data during backup operations.

 

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About nicoljako

CTO of Exelegent, sysadmin, architect of IT infrastructures​
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