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</o:shapelayout></xml><![endif]--></head><body lang=EN-NZ link=blue vlink=purple><div class=WordSection1><p class=MsoNormal style='margin-left:5.25pt'><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> rrd-users-bounces+s.shipway=auckland.ac.nz@lists.oetiker.ch [mailto:rrd-users->bounces+s.shipway=auckland.ac.nz@lists.oetiker.ch] <b>On Behalf Of </b>Ryan Kubica<br></span><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'>><o:p></o:p></span></p><p class=MsoNormal style='background:white'><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'> >2) don't bother with rrdcached ( it's slow, adds complication, so just adds an intermediate <o:p></o:p></span></p><p class=MsoNormal style='background:white'><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'> >buffer (with it's own IO) which doesn't serve a useful purpose )<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt;background:white'><span style='color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I would, in general, disagree with this (“rrdcached is slow”); it really comes down to how you configure it.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I’ve done a number of tests for performance of MRTG + RRDTool + rrdcached to see the relative performance of different versions and options. The benefit of rrdcached is heavily dependent on how aggressively it is configured; if you set it to cache minimally then you have little benefit, if any. However, a more aggressive configuration (>5 steps cache time) will give you gains as it updates the files less frequently. Of course, it depends again on how often you are reading the files now, as reading via rrdcached forces a flush and you lose any additional benefits that would be accrued over the remainder of the caching window.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Another benefit of rrdcached (at least for MRTG users) is that it allows you to decouple your collector, frontend and backend so that you can have your RRD on one server (with a fast disk IO) but have multiple other servers collecting data and feeding it back via rrdcached over TCP. Similarly, frontend web servers displaying the data can pull it via rrdcached over the network.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Also, since the rrd client just has to pass over the data to rrdcached, and not wait for the actual write, return is much faster.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>However, on the downside, rrdcached is relatively immature – you need to use the trunk version to get all the functionality, the stable version is limited to update, fetch and graph. The security side can sometimes bite you when running over TCP. And, of course, you have to tune it and configure it correctly in order to get the maximum benefit, and there is as yet not so much documentation available on how to best achieve this.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Steve<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div><div class=MsoNormal align=center style='text-align:center'><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><hr size=2 width="100%" align=center></span></div><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Steve Shipway<o:p></o:p></span></b></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>ITS Unix Services Design Lead<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>University of Auckland, New Zealand<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Floor 1, 58 Symonds Street, Auckland<o:p></o:p></span></p><p class=MsoNormal><i><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";color:#595959'>Phone: +64 (0)9 3737599 ext 86487<o:p></o:p></span></i></p><p class=MsoNormal><i><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";color:#595959'>DDI: +64 (0)9 924 6487<o:p></o:p></span></i></p><p class=MsoNormal><i><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";color:#595959'>Mobile: +64 (0)21 753 189<o:p></o:p></span></i></p><p class=MsoNormal><i><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";color:#595959'>Email: <a href="mailto:s.shipway@auckland.ac.nz"><span style='color:#595959'>s.shipway@auckland.ac.nz</span></a><o:p></o:p></span></i></p><p class=MsoNormal><span lang=EN-GB style='font-size:18.0pt;font-family:Webdings;color:green'>P</span><span lang=EN-GB style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:blue'> </span><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial Narrow","sans-serif";color:green'>Please consider the environment before printing this e-mail</span><span lang=EN-GB style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:blue'> </span><span lang=EN-GB style='font-size:7.5pt;font-family:"Verdana","sans-serif";color:navy'><o:p></o:p></span></p><p class=MsoNormal><i><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></i></p></div><div style='border:none;border-left:solid blue 1.5pt;padding:0cm 0cm 0cm 4.0pt'><div><div><div><p class=MsoNormal style='margin-bottom:12.0pt;background:white'><span style='color:black'><o:p> </o:p></span></p></div></div></div></div></div></body></html>