Error:

A job failed with systems error e00084f4 unknown error (V-79-57344-34036)

Problem description:

There have been multiple instances in which a setting called the RetryBusyCount setting is set too low and this leads to the failure of the backup jobs.  See below for instructions in order to make the registry change on the backup server.  The original setting calls for a value set at 75 decimal,  but it is recommended to change it to 100 decimal or 64 hex,  as is needed in the registry entry.

NOTE:  Please back up the current registry before making this change to preserve the original version. Be careful when making any registry changes as this can cause serious problems.

If the backup jobs continue to fail, then it is recommended to set this value higher,   It is feasible to have this configuration setting set as high as 250, until the issue is resolved.  If issue persists at max value of 250,  then further troubleshooting steps would be in order to determine the source,  causing the failure. Your registry entry would be under the LTO-4 and not the LTO-3 as shown below.

Solution:  To resolve the media write errors, the following steps were taken to modify the registry in Windows on the media server.
1)  Launch regedit by click start, run and type regedit, click ok

2) Browse to  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\SCSI\[device identifier name for the tape LTO-3 tape device]\[numeric device instance id for the LTO-3 tape device]\Device Parameters\

3) Add a key named Storport under Device Parameters (if one does not already exist).

4) Add a key name called BusyRetryCount. The key type is REG_DWORD, and the value should be set to 4b hex (75 decimal).

5) Close regedit

6) Reboot the server

Should do the trick. Worked perfectly when we experienced the issue.

Source: Symantec