Sans Digital ER208UT+B, Руководство пользователя

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APPENDIX
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The RAID subsystem allows user to choose the task priority (Ultra
Low (5%), Low (20%), Medium (50%), High (80%)) to balance
volume set access and background tasks appropriately. For high
array performance, specify an Ultra Low value. Like volume ini-
tialization, 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 subsystem firmware
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
bad sectors without external help using cyclic redundancy check
(CRC) checksums stored at the end of each sector.
RAID subsystem drives perform automatic defect re-assignment
for both read and write errors. Writes are always completed - if a
location to be written is found to be defective, the drive will auto-
matically relocate that write command to a new location and map
out the defective location. If there is a recoverable read error, the
correct data will be transferred to the host and that location will
be tested by the drive to be certain the location is not defective. If