Summary
Consider the following Scenario: A large backup job with many tasks is one of many jobs running over a period of time (such as a weekend) and this backup has the destination options 'Set original offsite' and 'Early drive release (EDR)' set to 'yes'. It is seen that the offsite backup job used more media than a regular job and the media was not used to full capacity in some cases.
Resolution
'Early drive release' is an option to allow the software to maximize the use of tape drives when running multiple jobs, so when a task has completed the drive can be released for use with another job. 'Mark original Offsite' is an option to mark the media that is to be removed and stored offsite. Consider the difference in behavior when using these options:
With destination option 'Early Drive Release' set to 'No' and 'Mark original Offsite' set to 'Yes':
The backup job will pick up and retain the tape drives for the duration of the job. Hence the media that are picked up by the job will be used until they are full (in which case another is mounted for use) or the job completes. Media is set to 'offsite' only when the media is full or the job completes.
With destination option 'Early DriveRelease' and 'Mark original Offsite' both set to 'Yes':
If only one job is active, to prevent the case of releasing and reacquiring same device at end of each task, early drive release is deactivated, and operation is the same as above. However, if another job becomes active at the same time as the offsite job, then early drive release is honored. In this case, at the end of a task the tape drive is released and at this point the media is marked offsite (even if not full). Media marked offsite is not available for use (until this status is reversed), therefore another available media is mounted. Thus the offsite backup job will end up using more media than the previous case.