SQL Server Backup – How to Backup a VM with SQL Server

I would add TRY/CATCH blocks to handle errors and log them. The DB could be in single user, being restored or whatever.

Without this, errors can abort in a way that no errors are logged (statement, batch, scope, connection etc)

With TRY/CATCH then everything except for compile or connection aborting errors are logged? but I doubt this is the case.

I'd also use sys.databases which replaces sysdatabases and read more flags:

-- declares etc

BEGIN TRY

    DECLARE db_cursor CURSOR FOR  
    SELECT name, state, user_access
    FROM sys.databases 
    WHERE name NOT IN ('tempdb')

    OPEN db_cursor   
    FETCH NEXT FROM db_cursor INTO @name, @state, @user_access

    WHILE @@FETCH_STATUS = 0   
    BEGIN   

        SET @fileName = @path + @name + '.bak'
        IF @state = 0 AND user_access = 0
        BEGIN
            BEGIN TRY
                BACKUP DATABASE @name TO DISK = @fileName  WITH INIT
            END TRY
            BEGIN CATCH
                -- log but do not rethrow so loop continues
            END CATCH
            WAITFOR DELAY '00:00:20'
        END
        ELSE
           --log user and/or state issues

        FETCH NEXT FROM db_cursor INTO @name 
    END   

    CLOSE db_cursor   
    DEALLOCATE db_cursor

END TRY
BEGIN CATCH
  -- some useful stuff here
END CATCH

This KB isn't directly related but the quote in it is:

MSKB2615182: Windows Server Backup May Fail Because of the SQL VSS Writer:

When Windows Server Backup attempts to backup a disk volume, a Volume Shadow Copy Snapshot is created for the volume. When the snapshot is created any VSS writer associated with the volume is called.

If there are SQL Server VSS writer backups being taken then you will see records in the MSDB.dbo.BackupMediaFamily table in the physical_device_name column. You might want to look into disabling the SQL Writer Service.

TechNet: SQL Writer Service