We have a server running incremental backups four times a week, and full backups once a week. It has been reporting hardware errors, intermittently but more frequently as of late:
Error: The device reported an error on a request to read data from media.
Error reported: Hardware failure.
There may be a hardware or media problem.
Please check the system event log for relevant failures.
Error: C: is not a valid drive, or you do not have access.
The hardware guys have replaced all hardware: VXA tape drive, SCSI cable, SCSI card, SCSI terminator, riser card, and system board, and the error is still occurring. Are there ever cases of incorrect reports like this, or could there be another hardware problem? Like I said, it's intermittent, so I don't see how it could be a permissions issue either.
EDIT: The system event log is reporting the following errors:
(Event ID 9)
The device, \Device\Scsi\adpu3201, did not respond within the timeout period.
(Event ID 117)
The driver for device \Device\Scsi\adpu3201 detected a port timeout due to prolonged
inactivity. All associated busses were reset in an effort to clear the condition.
It reports those two errors three times in a row, about eight minutes apart, before finally failing. The tapes have also been replaced and drivers have been updated.
The error message is saying C:, not the tape drive. So let's break out both possibilities in the error message:
"C: is not a valid drive." Is C: a single drive? A RAID? Is there anything that might be eating disk IO at the same time as your backups? (For that matter, is there anything eating your CPU or memory at that time?) Like longneck said in his comment, are there any controller firmware or driver updates for the C: drive's hardware? If it's a RAID, have you checked the drives and the RAID controller? (Some kinds of RAID--5, for example--have degraded read performance with a bad drive that can interfere with backups.)
"Or you do not have access." What account/privileges does the backup run as? If it's System, aka COMPUTERNAME$, could it be changing its password at that time? If it's another account, does it have network connectivity to verify the credentials it's using? Is this a service account where someone has entered the password wrong somewhere else, causing a lockout during your backup? Is one of your domain controllers having an issue?
Do try replacing the tapes, like Michael Hampton suggested above, because it's easy. But I don't think that's your issue.
We looked over the logs more and figured out there were a handful of tapes that were consistently failing. Turns out the hardware guys were not replacing the tapes with new tapes, just shuffling the tapes they already had. Getting brand new tapes resolved the problem entirely.