About Background Taskswww.3ware.com 169About Background TasksBackground tasks are maintenance tasks that help maintain the integrity ofyour drives and data. These tasks include Initialization of new units Rebuilds when units have become degraded Unit verification Migration of an on-line RAID from one RAID configuration to another Self-testsAbout InitializationSome RAID levels must be initialized for best performance. (For specifics,see “Initialization of Different RAID Types” on page 170.) Initialization cantake place before the units are put into service (foreground initialization) orwhile the units are being used (background initialization).Initialization makes parity information valid. Foreground initialization doesthis by simply writing zeroes to all the drives so that they all have the samevalues. Background initialization uses an algorithm to perform initializationand does not rewrite existing data.Foreground Versus Background InitializationA foreground initialization is run from the BIOS using 3BM. It clears allexisting data from the drives. Foreground initialization can take several hours,depending upon the size of the unit. After foreground initialization completes,you can start the operating system and units will perform at peak efficiency.If immediate access to the unit is important, you can stop foregroundinitialization by pressing Esc and boot to the operating system. Backgroundinitialization will then start automatically within about 10 minutes.Background initialization does not write zeroes to the drives or harm yourdata, so you can partition, format, and use the unit safely. For the 9000 series,the unit is fully fault-tolerant while the initialization takes place. That is, ifthe array degrades before the initialization is complete, the data willremain intact.When initializing is done after booting to the operating system, the process ofinitializing takes longer than it does if initialization is done by writing zeroesto the unit in the BIOS. Consequently, it will be a longer period of time untilthe performance of the unit is fully optimal.Although you can use the unit while it is being initialized in the background,initialization does slow I/O performance until completed. You can adjust howmuch initialization will slow performance by setting the rate at which it
