[rrd-users] Multiple Updates Per Second

Steve Shipway s.shipway at auckland.ac.nz
Thu Oct 4 00:29:10 CEST 2012

Rrdcached has more effect as you increase the caching time.

IE, if you set it to cache for 30min, and your update for a given RRD file is every 5min, then you should end up making about 1/6th of the disk IO (actually a bit more than that due to RRA rollups, but its a good rule of thumb)

The people with huge update rates seem to be doing this --
1. big cache times, like an hour or two
2. caching in memory (and a lot of memory available to use)
3. journal (which you need if having a big cache time) on very fast disk
4. high update-to-rrd rate, IE updating one rrd every minute is more efficient than updating 5 rrds every 5min if using rrdcached

This is how we run rrdcached (~60 updates per second)

/u01/rrdtool-1.4/bin/rrdcached -b /u01/rrddata -s mrtg -m 0666 -z 60 -p /var/tmp/rrdcached.pid -t 4 -j /u01/rrddata/journal -w 1800 -O -a 6 -l unix:/var/tmp/rrdcached.sock -l rrdserver.auckland.ac.nz -l localhost

We only cache for 30min ( -w 1800 ).  Note we increase the write threads ( -t 4 ) from the default of 1 which might be a good idea for you to consider -- you may be bottlenecking on this?


Steve Shipway
ITS Unix Services Design Lead
University of Auckland, New Zealand
Floor 1, 58 Symonds Street, Auckland
Phone: +64 (0)9 3737599 ext 86487
DDI: +64 (0)9 924 6487
Mobile: +64 (0)21 753 189
Email: s.shipway at auckland.ac.nz
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