When you try to run a backup, it fails with the error "Application writer's data is not available. Please check the application writer status."
Internal log files will show the error code: ZWC_ENG_ERR_NO_WRITER_DATA
What's going on?
Zmanda Cloud Backup utilizes a built-in Windows function known as Volume Shadowcopy Services, or VSS. Every backup type in ZCB relies upon one or more VSS Writers. Each writer is controlled by a Windows Service.
A list of currently available writers can be seen via the command line on any Windows machine. Open a 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.
If one or more writers required for backup is unavailable, the backups will fail with the error: Application writer's data is not available. Please check the application writer status.
A list of writers required for each backup type, and the controlling service for each, can be found here:
Determine which writer is missing by using the vssadmin list writers command, and enable it.
Common missing writers
Microsoft Exchange Writer
The Microsoft Exchange Writer is off by default on Small Business Server 2003 machines. You must enable the writer as shown in this Microsoft article: http://support.microsoft.com/kb/838183
Sharepoint requires three separate writers, and all must be enabled.
Additionally, the Sharepoint Foundation VSS Writer Service must be registered before it will function. Please see this Microsoft article for Sharepoint 2010. Similar articles are available online for other versions of Sharepoint.
If your System State writer is missing on Windows Server 2008, please see System State backups fail and the System Writer is missing.