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Removable Storage is the foundation for the way Windows Server 2003 manages tapes, data DVDs and other removable media. While data management applications manage the data, Removable Storage service allows several applications to share the same storage resources. Specifically, the Windows Backup tool (NTBackup.exe), the most common method of backing up Windows Server 2003, relies on Removable Storage. If anything happens to Removable Storage during a backup operation, the operation will probably fail.
One such failure occurs with the message:
The device reported an error on a request to write data to media. Error reported: Invalid command. There may be a hardware or media problem Please check the system event log for relevant failures.
In addition, the name of the backup may change to a number. If you try to restore data from that backup, the restoration will fail.
What has happened is probably that the NTBackup couldn't find the Removable Storage service at some point during the backup. This happens most commonly when Removable Storage is stopped and re-started during the backup.
NTBackup uses Removable Storage to handle some parts of the backup job. If Removable Storage stops during a backup, it may close the communication handle that links NTBackup and Removable Storage If NTBackup makes calls to Removable Storage after Removable Storage has been closed, the calls will fail and NTBackup stops the job and may generate an error message.
In that case, Removable Storage service may also mark the partition being backed up as unrecognizable and replace the media name with a number.
The best cure for the problem is to not stop Removable Storage service during a backup job. If you already have the error, you should start from scratch and make a new backup.
Microsoft discusses the issue in a Knowledgebase article, http://support.microsoft.com/default.aspx?scid=kb;en-us;903007.
Rick Cook has been writing about mass storage since the days when the term meant an 80 KB floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last twenty years, Cook has been a freelance writer specializing in storage and other computer issues.