Help me to Analyse the Performance and get to the Root cause

[Anton Chigurh]

(05-14-2014 03:58 PM)GreenGecko Wrote:  No, a CDN will not affect TTFB, but - once again - the locality and size of pipe will affect delivery performance.

We can tit for tat all day, but the main point you seem to still be missing is I am saying if your site is optimized, and it's a small site anyway, you don't NEED a CDN. NEED being the operative word.

And the size of the pipe really is irrelevant if the internet service of the visitor is small pipe, and especially if there is a TTFB problem needing addressed. If you know a CDN won't help TTFB, why recommend it then? Let's fix the fat site and the TTFB problem first, is my idea.

I do not deal in theoretical, ephemeral high brow concepts when it comes to helping someone with their slow site. I stick to the objective concrete, nuts and bolts, SIMPLE things the person can do himself - right away - to improve performance. I do not say stuff like, "I don't know, maybe it's this maybe it's that" like you had in your first reply to this thread. I go right to the meat of a situation with things I KNOW about, that help.

I could show you a dozen examples of sites I have optimized for people which had CDNs on them when the work started and were terrible performers, which now are excellent performers globally and don't use a CDN any longer. I am not speaking from theory, I am speaking from experience of actually optimizing many sites.

There's no reason for us to quibble and fight, we're both trying to help people, volunteering our time and asking for nothing in return. Hopefully you can respect that too.

(05-15-2014 12:28 AM)pmeenan Wrote:  If you are serving content to a fairly small region (within just the US, Just within Europe or even a single country) and your server is hosted fairly centrally to that region then a CDN isn't necessary and may actually hurt things. If you are serving traffic globally then a CDN is CRITICAL to performance.

When you start talking about India (or Australia) -> US you start getting round trip times on the order of 1/4 second. Every socket connect and request has to pay that round trip cost but the real killer is in TCP slow start. For each new connection you can only deliver 4-15KB (depending on server TCP config) before having to make another round trip and it doubles for each additional round trip. Delivering a useful amount of content ends up requiring a lot of those round trips and your get fetch times measured in seconds even for small resources.

CDNs can also provide a lot of other helpful services that aren't directly related to the perf of serving a single page but do seriously affect the scalability of the system. If you serve a lot of static content you can offload all of that bandwidth (and qps) onto a CDN which gives you a lot fewer servers to manage. They can also provide "evergreen" failovers to static pages in the case that your origins go down.

Yes, you are handing off some responsibility and adding a dependency but all of the major CDN's tend to have better uptime than individual hosting (or your upstream providers).

You shouldn't use them as a crutch because they can't solve the "10MB and 400requests" problem (though they will make it look better in something like keynote or gomez) but they are an absolutely critical part of a high performance global site.

Thanks for this clear and informative, objective assessment of the CDN situation Patrick. You went right to the heart of the matter for me - way too many people think a CDN is a "magic bullet" for every ill a site might have, recommend a CDN in knee-jerk fashion, and too many people take that advice thinking they fixed everything. People tend to gravitate towards the quick and easy solution when really they need to roll up their sleeves and go to work actually optimizing their site.




The OP wanted to know the root cause of his problems. I defined the root cause correctly, as a fat page. He slimmed the page down and improved the issues - he need only slim it down some more to see further improvement.