Max, you've not said what flavour of Linux you're running and this is relevant if you want to use sar as some distros are more up to date than others. I'll assume Redhat.
Redhat (and therefore CentOS too) ship a very old version, 7.0.2-3 - about 2.5 years old - and it's missing a lot of features. Not to mention that Redhat's implementation is quite crap. The init script provided to start the sadc data collector is only half written and what's there doesn't work at all. It has no interval on the command line which causes it to exit immediately without doing anything, and it should also be run in the background. God knows what the person who wrote that script was smoking, but it's an embarrassment. If you look you'll find that some daily data is being collected already in /var/log/sa. The sadd files (where dd = the day of the month) contain data collected for 1 second every 10 mnutes, and the sardd files are reports created from the day's data. You'll find that this data is being generated from a cron job here:
/etc/cron.d/sysstat.
I'd stop this fron running, clean out the files in /var/log/sa and set up sadc to run correctly. Note: By default sadc won't collect any disk data unless you run it with the -d flag.
In fact, I'd get rid of the supplied sysstat package and download the latest version from here:
http://pagesperso-orange.fr/sebastien.godardThe new version comes with a replacement for the sar datafile reader called sadf that can write reports in a number of different output formats: CSV, XML, etc. There's also a tool in the new kit called isag (Interactive System Activity Grapher) that can read the binary datafiles and produce graphs from them.
Hope this helps.
