Smart Mode - Accusys A12T3-Share User Manual

In the event of performance degradation or delay of a single drive due to aging, the RAID
system reads both data and parity stripes concurrently. It bypasses the slow reads and returns
data to the host with the regenerated data and to provide stable performance based on the
RAID parity.
Note
Slow response of some hard disks can be tolerated in DLP mode, you
may use S.M.A.R.T. function to check the conditions of hard disks in an
array and replace the faulty ones.
4.5.2 NCQ
Native Command Queuing (NCQ) is an extension of the Serial ATA protocol allowing hard disk
drives to internally optimize the order in which received read and write commands are executed.
This can reduce the amount of unnecessary drive head movement, resulting in increased
performance (and slightly decreased wear of the drive) for workloads where multiple
simultaneous read/write requests are outstanding.
The figure above illustrates the access sequence in NCQ and non-NCQ mode. The content
sequences of the two hard disks are the same: 1, 2, 3, 4. However, the access sequence in
NCQ mode may vary to improve the performance.
4.5.3

SMART Mode

S.M.A.R.T. is a monitoring system of disk drives to detect and report on various indicators of
reliability, in the hope of anticipating failure. Accusys RAID system supports S.M.A.R.T. Once
this function is selected, you can select the check interval from the drop-down list. Choose from
1 minute to 8 hours for SMART Mode to be active. The RAID controller will command each hard
disk to perform S.M.A.R.T. according to the check interval selected. The check results will be
shown as an Event message in the main menu.
When running S.M.A.R.T. mode, the performance of the system will be slightly affected. The
higher the check frequency, the more the sequential accesses are affected. It is recommended
to turn off S.M.A.R.T. if high performance required. On the other hand, running S.M.A.R.T.
constantly allows you to monitor the conditions of hard disks at any time.
The options of time to check disk's S.M.A.R.T are 1,15,30,60 minutes and 2,4,8 hours. We
strongly suggest set to 8 hours. Frequently checking will reduce the life time of hard drives
User Guide
5. RAID
Page 4-9