[collectd] collectd & rrdcached scalability issue

Stefan Wiederoder stefanwiederoder at googlemail.com
Tue Oct 2 10:29:01 CEST 2012

Hi Bostjan,

I´m currently storing my rrd´s on a RAM-disk, therefore I would think that
it´s not an IOPS problem.

these are my rrdcached options:
OPTIONS="-m 775 -s rrdcached -l unix:/tmp/rrdcached.sock -l /var/run/rrdcached/rrdcached.pid -b
/opt/collectd_data -F -j
/opt/collectd_journal -t 16"


2012/9/8 Bostjan Skufca <bostjan at a2o.si>

> Hi Stefan,
> I know this may not be the solution you are looking for, but:
> How about using socket of rrdcached daemon and instructing it to flush the
> data of immediate interest (rrds you are about to view)?
> Works well for me on ganglia installation which uses rrdcached to cache up
> to three hours of data...
> What are your RRDcached settings? How much IOPS can you storage subsystem
> handle? SSD as a fast-paced fix? Do you have a graph of IOPS for your
> collectd host?
> b.
> On 7 September 2012 09:16, Stefan Wiederoder <
> stefanwiederoder at googlemail.com> wrote:
>> Hello list,
>> my current collectd (v4.10) installation is using rrdcached (rrdtool
>> 1.4.4), which worked fine
>> so far. But with the number or hosts growing beyond 1000 it seems to have
>> a negative impact
>> on my central collectd server.
>> I´ve 37 GB of data (residing in a RAM-disk), plus 12 GB of journal data.
>> Each hosts has a
>> minimum of nine plugins activated, but max is only two or three more on
>> some special boxes.
>> the problem is that collectd data seems to lag "behind" the longer
>> collectd/rrdcached is running.
>> this accumulates up to three hours a day until the daily restart kicks
>> in. An example, I see data
>> from 12h when I look at graphs at 15h.
>> this was not a problem with fewer hosts (< 900), it´s been getting worse
>> with more and more hosts.
>> I´ve only specified the number of write_threads so far (=16), but no
>> other parameters.
>> do you have any suggestion for me?
>> thanks
>> ,
>> Stefan
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