Avago Technologies 3ware SAS 9750-16i4e - Manual (Page 175)

Scheduling Background Tasks
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Figure 82. Background Task Rate on Controller Settings page
The furthest left buttons set the firmware to the fastest rebuild and verify
settings. This means that maximum processing time will be given to
rebuilds or verifies rather than I/O. The furthest right buttons set the
firmware to the slowest rebuild and verify settings, giving maximum
processing time to I/O.
After you select one of the radio buttons, the page refreshes, and a
message at the top confirms the change you have made.
Background Task Prioritization
Although migration tasks follow the same schedule as rebuild and
initialization tasks, they are always given the highest priority because of the
controller and disk resources required during migration.
Once a unit is put into the migration state, it must be allowed to complete the
process. While migrating, rebuilds or verifies to the unit are not permitted.
Rebuilding preempts verify operations. If a unit requires rebuilding, that
process will take place before the unit is verified.
Controllers can work on multiple units at the same time. This means that if
you have both a redundant unit and a non-redundant unit, the verification of
the redundant unit and the media scan of the non-redundant unit will occur at
the same time.
Scheduling Background Tasks
You can set up scheduling windows for when background tasks occur so that
routine maintenance of storage media occurs when it will be least likely to
interfere with day-to-day work on the system (peak I/O times). By creating
and using schedules, you can specify when active rebuilding, migrating,
verifying, and testing of units should occur. For example, you might wish
these tasks to occur at 2 AM each day, or on weekends.
Note: Initialization follows the rebuild/migrate schedule. The default setting for both
is to ignore the schedule.