NetBackup downs a drive automatically when read or write errors surpass the threshold within the time window. The default drive error threshold is 2. That is, NetBackup downs a drive on the third drive error in the default time window (12 hours).

Common reasons for write failures are dirty write heads or old media. The reason for the action is logged in the NetBackup error catalog (view the Media Logs report or the All Log Entries report). If NetBackup downs a device, it is logged in the system log.

You can use the NetBackup nbemmcmd command with the --drive_error_threshold and -time_window options to change the default values.

Additional information about nbemmcmd is available.

See the NetBackup Commands guide.

To reverse a down action, use the NetBackup Device Monitor to set the device to Up.