[collectd] RRDs on SSD - performance degredation [resend without images]

[Mariusz Gronczewski]

2013/9/10 Thomas Harold <thomas-lists at nybeta.com>

> On 8/16/2013 4:14 AM, Cyril Feraudet wrote:
>
>> 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"
>> </Plugin>
>>
>> After :
>> LoadPlugin rrdcached
>> <Plugin rrdcached>
>>   DaemonAddress "unix:/var/run/rrdcached/**rrdcached.sock"
>>   DataDir "/var/lib/collectd/rrd"
>>   CreateFiles true
>>   CollectStatistics true
>> </Plugin>
>>
>> Cyril
>>
>>
> How do you deal with the options:
>
> RRARows 20000 # PDPs = timespan / (stepsize * rrarows)
> RRATimespan 320000 # 3.7 days (16s)
> RRATimespan 1600000 # 18.5 days (80s)
> RRATimespan 8000000 # 92.6 days (400s)
> RRATimespan 80000000 # 926 days / 30.5 months / 2.54 years (4000s)
>
> Which are normally placed inside of <Plugin rrdtool></Plugin>?
>
>
You *could* just bump up flush timers in rrdtool plugin like that:


<Plugin rrdtool>
    DataDir "/var/lib/collectd/rrd"
    CacheTimeout 1200
    RandomTimeout 600
    CacheFlush   1600
</Plugin>


which should result big reduce of writes done. Files can be still flushed
"on demand" by collectd's socket interface.

In my setup I run one collectd that just have network and rrdtool plugin
enabled and all other servers write to it, so I can avoid restarting it for
any config change

Also, what  filesystem do you use? Any kind of COW FS tend to have garbage
performance on RRD files just because they are mostly rewritten with small
amounts of data.



-- 
Mariusz Gronczewski (XANi) <xani666 at gmail.com>
GnuPG: 0xEA8ACE64
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