Installation guide

Software Operation Manual
194
Buffer Threshold Setting
There are 4 options in this new feature; 5%, 25%, 50%, 75%. The percentage
represents how much data should be kept in resident cache memory (how full
cache should get) before controller starts to flush data onto the hard drives. If
the buffer is set for 25%, then all 25% will be cached and is used for writing data.
The remaining cache memory will be used for reading and other system
overhead. Write buffer threshold for 5% is added for video recording. This
option will push data to disk early.
This feature gives controller extra buffer time in case of slow response from the
hard drives within a given time. Consequently, this can prevent a pause in data
flow and there will be continues data access and stream. This feature is very
useful for the video streaming applications where there is high demand for
constant non-stop data flow with no interruption due to lower performance of
specific hardware.
Amount Of Read Ahead
Read-Ahead data is buffered in the RAID controller cache, however, thereby
cutting down on the amount of I/O traffic to the disk. The Amount of Read Ahead
defines how many data of reading at a time, making more efficient use of the
RAID subsystem. This makes it possible to locate and re-issue the data without
repetitive hard parsing activities.
The Amount of Read Ahead parameter is used to allocate an amount of memory
in the cache memory the frequently executed queries and return the result set
back to the host without real disk read execution.
Default value is Auto: Controller will base on the HDD number to set the amount
of Read Ahead value. You can select between 512B ~ 14MB.
To decide how to set AV stream parameter, you need to check the Number of
Stream, Amount of Read Ahead, and Total Cache Memory during runtime. You
can try to adjust the three numbers to get the best performance as your
requirement. Number of Stream shows the number of stream added to the
system, Amount of Read Ahead shows the amount of Read Ahead data taken
from the cache without real disk execution, and Total Cache Memory shows the
total available memory being installed in the RAID controller. The following is the
rule of optimized setting for the AV Stream Playout application.
Number of AV Stream x Amount of Read Ahead X 3< Cache Memory installed in
the controller