When things go wrong with your data backups, it is critical that you address the problem right away. So, it is important to understand backup software error messages.
Unfortunately, each vendor that makes backup software uses its own individual error messages, so there isn't one comprehensive list of error messages that's applicable to every backup application. The following is a list of some of the more common backup errors and their causes. Keep in mind that your backup software may not use this exact wording when displaying error messages, but it will likely be some variation of it.
Network path not found
Generally speaking, this "network path not found" indicates that the backup software was instructed to back up a particular file or folder on a network drive, but that file or folder doesn't appear to exist. This error message can indicate that the file or folder in question has been deleted, but it doesn't necessarily mean that.
I recently encountered this error message when the server that was being backed up crashed (the blue screen of death) during the backup process. The crash caused all of the files and folders that hadn't been backed up yet to be inaccessible to the backup software. This error message can also be caused by network connectivity problems and power failures.
A common variation of this particular error message is "The specified network name is no longer available."
The requested resource is in use
"The requested resource is in use" message is used in a couple of different ways. Most backup applications use some variation of this error message to indicate a particular file is open, and therefore can't be backed up. There are, however, some backup applications that use this error message to indicate that the tape drive is in use by another backup operation.
I/O error
The dreaded I/O error usually means that the backup software either had trouble reading or writing data to the tape. Sometimes (depending on the individual backup application), this message can be caused by dirty tape heads, and cleaning the tape drive will fix the problem.
However, this error message frequently is caused by a critical hardware failure. For example, a SCSI controller may have gone bad, or a cable might be loose. If this is the case, then there is almost always a corresponding error message in the Windows system log. Windows system log entries can often help you troubleshoot the problem.
CRC error
A cyclic redundancy check (CRC) error basically means that data being read from or written to the tape failed an integrity test. This problem is almost always caused by dirty tape heads, but a faulty SCSI cable or a defective tape could also be to blame.
Access denied
The "access denied" error message is permissions related. It means that the account that the backup software is operating under doesn't have permission to open the file that is being backed up. If the backup software requires an agent to be installed on the backup target, then you need to make sure that the agent's service account has full access to the volumes that are being backed up.
The target machine has refused the connection
This error message is a tricky one. Most enterprise-class backup applications run on a centralized server, but require an agent component to be installed on any server that is being backed up. This type of error message typically occurs when the backup application has trouble communicating with an agent on another server.
There are a couple of things that can cause this problem. First, check to see if the agent service is running. If the agent is running, then you should check to make sure that the server that the agent is running on still has network connectivity, and that a firewall isn't blocking the port used by the agent.
About the author: Brien M. Posey, MCSE, has previously received Microsoft's MVP award for Exchange Server, Windows Server and Internet Information Server (IIS). Brien has served as CIO for a nationwide chain of hospitals and was once responsible for the Department of Information Management at Fort Knox. You can visit Brien's personal website at www.brienposey.com.
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