How to Resolve VSS Writer Errors

What are VSS Writers?

VSS writers are a function of the Volume Shadowcopy Service, a Windows service which allow for backups or snapshots of files or volumes to be made even while locked or in use. Many, if not most, enterprise and mid-level backup solutions on the market these days utilize VSS, so when you find your backups to be failing, it is often due to underlying issues with the Volume Shadow Service. 

When troubleshooting failed backups, one of the first places to look should be at the VSS writers since often times writers that are in a failed state will prevent backups from completing successfully. 

How to view VSS Writers:

To view the list of writers and the active state they are in, pull up a command prompt(as administrator) or PowerShell window and run the following command:

VSSAdmin list writers

This command displays a list of VSS writers and what state they are in. If you find any writers in an error state, you will need to find the corresponding service that it belongs to and restart that service. If the command hangs or does not return any data, this suggest that the VSS service or one of its dependent tasks is in a bad state, causing the VSS audit to fail. 

The writer name corresponds to a Windows service which Microsoft conveniently does not display in the results of the "list writers" command. You can cross reference the writers name with its service in the table below. Once the service is found, restart start it and then rerun the "VSSAdmin list writers" command. If the service is still in an error state or fails to restart, reboot the server. 

VSS Writer	Service Name	Service Display Name
ADAM $instanceName Writer	ADAM_$instanceName	$instanceName
ASR Writer	VSS	Volume Shadow Copy
BITS Writer	BITS	Background Intelligent Transfer Service
Certificate Authority	CertSvc	Active Directory Certificate Services
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
FSRM 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)	MSMQ	Message Queuing
MSSearch Service Writer	WSearch	Windows Search
NPS VSS Writer	EventSystem	COM+ Event System
NTDS	NTDS	Active Directory Domain Services
OSearch VSS Writer	OSearch	Office SharePoint Server Search
OSearch14 VSS Writer	OSearch14	SharePoint Server Search 14
OSearch15 VSS Writer	OSearch15	SharePoint Server Search 15
Registry Writer	VSS	Volume Shadow Copy
Shadow Copy Optimization Writer	VSS	Volume Shadow Copy
SharePoint Services Writer	SPWriter	Windows SharePoint Services VSS Writer
SMS Writer	SMS_SITE_VSS_WRITER	SMS_SITE_VSS_WRITER
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
WDS VSS Writer	WDSServer	Windows Deployment Services Server
WIDWriter	WIDWriter	Windows Internal Database VSS Writer
WINS Jet Writer	WINS	Windows Internet Name Service (WINS)
Windows Server Storage VSS Writer	WseStorageSvc	Windows Server Essentials Storage Service
WMI Writer	Winmgmt	Windows Management Instrumentation

For additional information on VSS and what services writers do, check out this article from Microsoft: In-Box VSS Writers