Proware EP-4643S2D2-F8S6, User Manual

Page: 119 / 151

Fibre to SAS/SATA Disk Array
User Manual 119
Buffer Threshold
This new feature there are 4 options; 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
512KB ~ 16MB.
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 needing 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 needing
great band widths. They are required to do some setting for the handshaking during
the processing of stream data. This setting is an object of transferring stream data
efficiently on an existing RAID controller. Normally you should not need to modify
this value. Default value is 6. You can select between 6~256.
To decide how to set AV stream playout 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.
Optimize AV Recording
AV recording option is for video recording (no time limit), but if used in normal
operation, performance may be degraded. This new feature there are 4 options;
Disabled, Mode1, Mode2 and Mode 3. Default value is Disabled. Our controller cache
uses LRU method, there have no special memory capacity reserved for read or write.
The Mode 1, 2 and 3 are used for define the command sorting method. The default