Buffer Cache Hit Ratio

[Steve Huizenga]

Does anyone know how I can see my buffer cache hit ratio?

[Sridhar Bhaskarla · Accepted solution]

Sar -b gives you buffer hit ratio.

#sar -b 2 10

Give %rcache and %wcache averaged every 2 secs
for 10 iterations.


-Sri

[Magdi KAMAL]

Hi Steve,

I agree with Sridhar,
#sar -b IntervalInSeconds NumberOfTimes

%rcache : Give you the read cache percentage.
%wcache : Give you the write cache percentage.
bread/s : Number of physical reads per second.
bwrit/s : Number of physical writes per second.
lread/s : Number of logical reads ( from buffer ) per second.
lwrit/s : Number of logical writes( to buffer ) per second.
pread/s : Number of reads per second from character device using the physio() ( Raw i/o ) mechanism.
pwrit/s : Number of writes per second to character device using the physio() ( Raw i/o ) mechanism.

Magdi

[Rick Bowles]

You can also see it in glance with "d" disk report, and "f" forward to page two of the disk report.

[Wodisch]

Hello,

to see the buffer hit rate as it was, say, yesterday,
you have to activate the "System Activity Data collector",
see the man page for "sadc" for this. It does contain the
"crontab" entries you need for this.
Thereafter you can call "sar -b" and see today's
statistics, or you may use the "start" and "end" options
to tell "sar" the timeframe you are interested in.

HTH,
Wodisch