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APPENDIX
ue as normal, however, the system performance and fault toler-
ance will be affected.
• Adjustable Rebuild Priority
Rebuilding a degraded volume incurs a load on the RAID sub-
system. The SATA RAID controllers allow the user to select the
rebuild priority to balance volume access and rebuild tasks ap-
propriately. The Background Task Priority is a relative indication of
how much time the controller devotes to a background operation,
such as rebuilding or migrating.
The RAID controller allows user to choose the task priority (Ul-
tra Low (5%), Low (20%), Medium (50%), High (80%)) to bal-
ance volume set access and background tasks appropriately. For
high array performance, specify an Ultra Low value. Like volume
initialization, after a volume rebuilds, it does not require a system
reboot.
High Reliability
•
Hard Drive Failure Prediction
In an effort to help users avoid data loss, disk manufacturers are
now incorporating logic into their drives that acts as an "early
warning system" for pending drive problems. This system is called
SMART. The disk integrated controller works with multiple sensors
to monitor various aspects of the drive's performance, determines
from this information if the drive is behaving normally or not, and
makes available status information to RAID controller rmware
that probes the drive and look at it.
The SMART can often predict a problem before failure occurs.
The controllers will recognize a SMART error code and notify the
administer of an impending hard drive failure.
• Auto Reassign Sector
Under normal operation, even initially defect-free drive media can
develop defects. This is a common phenomenon. The bit density
and rotational speed of disks is increasing every year, and so are
the potential of problems. Usually a drive can internally remap
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