[consulting] CDN question and recommendation

Mon Dec 14 23:27:41 UTC 2009

Really appreciated that. I had a general understanding of a CDN, but hadn't
given any thought to the downsides which expounded on.

-Dave

On Mon, Dec 14, 2009 at 6:45 AM, Michael Goldsmith <ixlr8 at comcast.net>wrote:

>  To answer your first question, yes.  A CDN will ease some of the
> performance issues you’ll have.  But it’s not always as simple as that.
>
>
>
> The long and short of it, is that it works something like this.  These are
> just broad strokes, and I’m probably missing some stuff here, but it’s
> enough to give you the gist of it.  OK, you hit a web page from New York.
> The web page is hosted in a data center in Dallas, TX.  Your request goes
> through a bunch of hops through various routers to get to the web server
> that hosts the page, it makes the request, and generally, the packets turn
> around go back through the same routers to get to your computer.  I say
> generally, in that sometimes they take alternate paths, but that’s beyond
> the scope of this explanation.
>
>
>
> Generally, this happens very quickly.  However, let’s say that you were in
> London, instead of New York.  Your request is going to go through a lot more
> hops than it would if you were in NY.  This takes longer to load your
> pages.  Also, if you’re serving a lot of static files- images, video-
> anything that doesn’t change very often, you’re pushing out these files over
> and over again to each person who’s making the request.
>
>
>
> So here’s where a CDN can make things easier for you.  A company, sets up a
> bunch of high powered servers all around the world.  And when a piece of
> content is made available to the CDN, it makes a copy on every one of the
> servers.  So if you’re making a request from London, it looks at
> cdn.example.com for the image, instead of example.com, and some fancy DNS
> rules tell it to make the request to the CDN server in London, instead of
> making the request to Dallas.  If it doesn’t find the piece of content on
> the local cdn server, then it defaults back to making the request from the
> server in Dallas.  Also, it eases a lot of load off of your web server,
> since most of your static files are hosted on other servers, they’re not
> hitting you for the load and bandwidth on your machine.
>
>
>
> There are a bunch of different ways to set this up.  The CDN module does a
> lot of the heavy lifting on your end to rewrite the urls of images.  As far
> as which method to use, that’s going to depend on how you set up with the
> CDN company.  Each company does things slightly different, so you’ll want to
> talk with them to figure out what is the best option.  I’ve found that
> they’re very helpful and will walk you through the process if you ask them.
> You might even be able to set up a reseller account with a specific company,
> so you can make some money on referrals.
>
>
>
> As far as specific CDN’s are concerned, it depends.  It depends on how much
> data you’re pushing, what kind of data you’re pushing, etc.  Some CDN’s
> don’t care what you’re pushing, others have some requirements.  It also
> depends on how much your client can afford.  Generally, larger CDN’s tend to
> cost more than smaller ones.  But they’ll probably have more servers on
> their network, so they’ll be faster.  I’ve found that the rule of thumb is
> that you get what you pay for.  You can get a CDN that costs about $20/
> month.  Or you can get one that costs $200/ month, or more.  You’ll see the
> difference, but it really comes down to what your client needs.
>
>
>
> Now I said that it’s not always as simple as that.  The caveat to this, is
> that let’s say you’re in NY, and you’re testing your site, and everything
> you see is fine.  Let’s say something gets corrupted, or cached wrong on the
> way to the London server, which happens every once in a while.  You won’t
> see what’s wrong, because everything you see is coming from the NY server.
> That’s an extreme case, but dealing with CDN’s can sometimes be a bit of a
> pain when you’re making changes to one of those files, say a CSS file, for
> example, and you’re clearing your Drupal cache, but the file is just not
> updating.  You’ll bang your head against a wall until you remember that you
> have to clear the cdn’s cache too, and then the files need to repopulate,
> which means a whole bunch of servers are going to be pinging your local
> server trying to get this new file while the new copy rolls out through the
> CDN, which can take a little while to do.  Hope you didn’t need to do that
> during a peak traffic hour…  I’m sure you see where I’m going with that.
>
>
>
> All in all, CDN’s are great if you can afford them, but there is definitely
> a price to pay for it.  If your client isn’t tech savvy and you’re not
> managing the site, they might have some difficulty wrapping their head
> around the concept, and sometimes there are weird hiccups that takes some
> esoteric knowledge to fix.  It doesn’t happen often, but it’s something that
> should be noted.
>
>
>
> *Thank you very much for your time and consideration,*
>
> *Michael Goldsmith*
> *(732) 619-6865 - mobile*
> *ixlr8 at comcast.net - email*
> *http://www.platypustheory.com <http://www.ixlr8.org/> - website*
>
>
>
> *From:* consulting-bounces at drupal.org [mailto:
> consulting-bounces at drupal.org] *On Behalf Of *Christian Pearce
> *Sent:* Monday, December 14, 2009 8:56 AM
> *To:* A list for Drupal consultants and Drupal service/hosting providers
> *Subject:* [consulting] CDN question and recommendation
>
>
>
> I have a potential customer that is going to have traffic from around the
> world.  It is my understanding a CDN will ease a lot of the pain while using
> the site.  First is this true?  Second I plan on using this module
> http://drupal.org/project/cdn, I imagine origin pull is going to be the
> best method.  Does anyone have experience using this?  Can you make a
> recommendation for a particular service to use?
>
>
> --
> Christian
>
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