Try it and you'll see. rrdcached write to disk on demand and at the
latest when the time specified is out. 

I/O may be decreased by 10 or more depending on the "interval" on
collectd side and the '-w' option on rrdcached side. 

There is no migration to plan. Just start properly rrdcached and
configure collectd, ex : 

/usr/bin/rrdcached -w 1800 -z 1800 -t 8 -p /var/run/ -l
unix:/var/run/rrdcached/rrdcached.sock -j /var/lib/rrdcached/journal 

And make sure the user used to run rrdcached is able to write rrd. 

One more thing : rrdtool graph command need to know the rrdcached socket
to flush data before graph them, ex: 

rrdtool graph --daemon=/var/run/rrdcached/rrdcached.sock -t .... 


Le 2013-08-16 11:19, Jesse Reynolds a écrit : 

> On 16/08/2013, at 5:16 PM, Cyril Feraudet <> wrote: 
>> Do you use rrdcached ? If not, use it and all you i/o problem will disappear.
> Sounds too good to be true :-) 
> Is the scheduling improved somehow? Is it more efficient with writing the RRD 
> files? It seems that it will still need to update the RRD files as the rrd 
> plugin does now, so not sure how this means there'll be less demands placed 
> on IO. 
> We're planning on switching to opentsdb but that may be a little way off. 
> I have looked at rrdcached. With switching to rrdcached, can you do this 
> while keeping the RRD files in place? Or is there a migration process? 
> Cheers 
> Jesse

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