rrdcached is a daemon and a Collectd plugin who replace rrdtool plugin.

There is no need to modify your architecture. Just install rrdcached and configure rrdcached Collectd plugin to work with.

Before :

LoadPlugin rrdtool
<Plugin rrdtool>
 DataDir "/var/lib/collectd/rrd"

After :
LoadPlugin rrdcached
<Plugin rrdcached>
 DaemonAddress "unix:/var/run/rrdcached/rrdcached.sock"
 DataDir "/var/lib/collectd/rrd"
 CreateFiles true
 CollectStatistics true


Le 2013-08-16 10:02, Vitaly Belousov a écrit :

Hello colleagues,

Does rrdcached work the same time as network? I've created server to collect data from several servers thru network plugin. Also I planned to use rrdcached to decrease io but I figured out that its not working same time when network plugin enabled.

Is it an open and well known issue, or its not an issue but the feature?


On Friday, August 16, 2013, Cyril Feraudet wrote:


Do you use rrdcached ? If not, use it and all you i/o problem will disappear.



Le 2013-08-16 00:39, Jesse Reynolds a écrit :


We're noticing some interesting patterns in collectd / librrd is flushing RRD files to disk.

We have a 1TB volume for RRD files, which is at 75% capacity. Over the last few weeks the response time of the disks has slowly degraded, with a few sudden jumps (see graph below). When it jumps up in response time, it seems collectd responds by halving the write ops, and octets. Is it just deciding to flush half as often? If anyone has some pointers to the details of this behaviour, that'd be great.

Also, does anyone recognise this pattern as being related to how full the SSD backed volume is, and perhaps the disks are now needing to do garbage collection? I'm pretty new to SSDs, and I suspect RRDs are a fairly uncommon way to utilise SSD drives.

FWIW, we have 5 x 256 GB Micron SSDs in a IBM hardware RAID 5 set. The OS is linux (ubuntu 12.04).

disk time, ms:

bytes per second:

RRD filesystem disk utilisation:

Thank you!

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[1] https://dl.dropboxusercontent.com/u/5932161/visage/disk%20time%20ms%201%20month.png [2] https://dl.dropboxusercontent.com/u/5932161/visage/rrd%20disk%20octets%20per%20second%201%20month.png [3] https://dl.dropboxusercontent.com/u/5932161/visage/rrd%20disk%20utilisation%201%20mth.png
[4] http://mailman.verplant.org/listinfo/collectd

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