Areca ARC-1882LP User Manual download pdf (Page 144)

WEB BROWSER-BASED CONFIGURATION

144

• Number of Retries

This setting determines the number of access that will be at-

tempted before the current command from the RAID controller

to the disk drive is aborted. You can modify the retry value by

entering a new value in the edit box beside this button and then

selecting the button. Normally you should not need to modify this

value. There are two selections, either 2 retry or 3 retry.

• Buffer Threshold

This new feature there are 3 options; 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 ush 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 sys-

tem 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 ow 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 ow with no interruption due to lower performance

of specic hardware.

• Amount of Read Ahead

Read-Ahead data is buffered in the RAID controller cache, howev-

er, thereby cutting down on the amount of I/O trafc to the disk.

The Amount of Read Ahead denes how many data of reading at

a time, making more efcient use of the RAID subsystem. This

makes it possible to locate and re-issue the data without repeti-

tive 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.

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Areca ARC-1882LP User Manual Page 144