Cache flushing techniques

Cache flushing methods

Idle cache flushing
Watermark cache flushing
Force cache flushing

If In general cache writes data to disk in small chunks  but the data which has to be written from the host end is very large then idle cache flushing cannot maintain LWM(low watermark level) in this situation watermark cache flushing kicks in

Watermark cache flushing try's to maintain cache between low and high watermark if It fails to bring cache below high watermark then force cache flushing kicks in disabling all write cache

Force cache flushing writes data to disk by disabling  all write cache till data in cache reaches LWM 
Only after then write cache is enabled

In the mean while data wot be written to cache and rather will be sent directly to disks resulting in low write performance

By default 
LWM - 20%
HWM - 80%