Installation guide

Chapter 4. Web Browser-Based Configuration
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4.8.2.4 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.
4.8.2.5 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 ~ 16MB.
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
4.8.2.6 Number of AV Stream
RAID controllers are required to have not only the function of processing ordinary
data but also the function of dealing with AV (audio/video) stream data which needs
real-time processing. Since the bus cycle used in RAID controller was designed to
transfer the computer data exactly, it was unsuitable for the transfer of AV stream that
needs a great band widths. They are required to do some setting for the handshaking
during the processing of stream data. This setting can adjust the efficacy of
transferring stream data on an existing RAID controller.