Avago Technologies 3ware SAS 9750-16i4e - Manual (Page 171)

Background Tasks
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Cancelling a Rebuild and Restarting It with a
Different Drive
When you start a rebuild from 3BM, you cannot cancel it in 3BM interface.
However, if you have drives in hot swap bays, you can remove and replace the
drive, rescan the controller (Alt-R), and then select a new drive to be used in
the rebuild. You can also boot the operating system, launch 3DM2, and cancel
a rebuild by using the
Remove Drive link on the Maintenance page.
If your drives are not in hot swap bays and you do not want to boot the
operating system and launch 3DM2, you can also cancel a rebuild by
powering down the system, physically removing a drive, and installing
another one that you want to use. Then when you start 3BM, the unit will
appear as degraded and you can rebuild it, using the steps described under
“Rebuilding Units through 3BM” on page 156.
Working with the Background Task Mode
Background Task Mode is specifically designed to address the issue of
latency, which can cause problems for some applications, by helping you
balance the rate of host I/O and efficient completion of background tasks.
About Latency and the Background Task Mode
Latency is the real or perceived delay in response time seen by the host
system when accessing some data. For some applications, such as streaming
video and audio application, it is important to minimize the latency of read
commands, so that users do not perceive a lag when viewing video or
listening to audio.
When background tasks are active (for example, rebuild, verify, and
initialization), there can be increased latency, and under some circumstances,
this can result in a degraded user experience or in an application failure.
You can set the Background Task Mode to minimize latency. This mode
monitors and paces the relationship between host I/Os and background tasks.
You can set the Background Task Mode to either
Adaptive (the default) or
Low Latency .
Low Latency mode minimizes the latency (delay) in reading data from the
RAID unit by slowing down the background task process. In contrast,
Adaptive mode allows the firmware to adjust the interaction of background
Note: If you want to pause the rebuild process through 3DM2, you can do so by
setting or changing the rebuild schedule on the Scheduling page. If you set a
schedule for rebuilds that does not include the current time, the rebuild process will
pause.