Buffer cache

 
Anoopkumar
Frequent Advisor

Buffer cache

Hi,

My production server has 64GB mem and 16CPUsc.sar out put showing w/io is high every time.(using EVA8100)
# sar 5 5

HP-UX sgen03 B.11.11 U 9000/800 06/30/10

10:57:31 %usr %sys %wio %idle
10:57:36 24 8 58 10
10:57:41 25 8 58 9
10:57:46 33 12 49 6
10:57:51 32 9 52 8
10:57:56 33 9 52 6

Average 29 9 54 8

I observed that our dbc_max value is very high its using around 10% of total RAM.

# kmtune |grep -i db
dbc_max_pct 10 - 10
dbc_min_pct 5 - 5

One of the HPUX best practice document says that its better to use 500MB buffer cache if the mem is more than 2 GB(IS it correct?)by setting Bufpages value.

SO I made one action plan.

1) Enable Async I/O

a) Enable the Async driver in OS
asyncdsk In
b) MAX_ASYNC_PORTS to 3000

2)use static buffer cache setting.

Kernel parameter Bufpages to 128000 (500MB)


If I enable async I/O will it use buffer cache more?

Please help me to solve this issue..

Thanks
Anoop