disk logging and sar

Jeremy J. Epstein jje at virtech.uucp
Tue Jan 9 01:52:01 AEST 1990

In article <9 at cimcor.MN.ORG>, mike at cimcor.MN.ORG (Michael Grenier) writes:
> I'd like to enable the 'sar -d' command for some block disk
> drivers I'm writing. How do I do this?
> Right now, sar -d doesn't give me anything.

Before you can use sar to show data, you must have collected the
data using sadc(1M).  The sadc(1M) man page gives some suggested
cron entries to generate the data at 20 minute intervals (too long
when debugging, but OK for normal monitoring).  Make sure that you
put the commands in the crontab file for 'sys', and set the permissions
for /usr/adm/sa appropriately.  Also, you probably want to initialize
sadc at boot time so you get a zero-point.

The other key thing once you're gathering data is updating the right
data structures (in your disk driver)...does anyone recall what
structures sadc reads to accumulate the statistics?

Another tool worth looking at is sadp, which can generate some nify
histograms and graphs of cylinder usage....
Jeremy Epstein
TRW Systems Division
2750 Prosperity Avenue

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