Lydia Leong

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Lydia Leong
Research VP
11 years at Gartner
19 years IT industry

Lydia Leong is a research vice president in the Technology and Service Providers group at Gartner. Her primary research focus is cloud computing, together with Internet infrastructure services, such as Web hosting, content delivery networks…Read Full Bio

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Rackspace Cloud Files (Mosso) + Limelight CDN

by Lydia Leong  |  November 20, 2008  |  1 Comment

It’s official: Rackspace’s Cloud Files can now be distributed via Limelight’s CDN.

The Cloud Files CDN works exactly like announced: drop your files into Cloud Files, push a button, have them served over the Limelight CDN. It’s 22 cents flat-rate, without origin fees. I’ve discussed this deal before, including in the context of Amazon’s CloudFront, and my previous commentary stands.

What will be interesting to see is the degree to which Limelight preserves infrequently-accessed content in its edge caches, vs. Amazon, as that will make a significant impact on performance, as well as cost-effectiveness vs. CloudFront. Limelight has a superior footprint, superior peering relationships, and much more sophisticated content routing. For people who are just looking to add a little bit of effortless CDN, their ability to keep infrequently-accessed content fresh on their edge caches will determine just how much of a performance advantage they have — or don’t have — versus CloudFront.

A Little Testing

In the spirit of empirical testing, I’ve created a Cloud Files account, too, and am now delivering the images of the front page of a tiny website from a combination of CloudFront and Cloud Files (which is under Rackspace’s Mosso brand).

It looks like my Cloud Files are being served from the same Limelight footprint as other Limelight customers, at least to the extent that I get the exact same edge resolutions for www.dallascowboys.com as I do for cdn.cloudfiles.mosso.com.

The Cloud Files deployment is reasonably elegant, and Mosso provides a GUI and thus is more directly user-friendly. You create a container (folder), drop your files into it, and click a button to make the files public, making them automatically and instantly available via Limelight. (The Amazon process is slower, although still within minutes.)

However, in a move that’s distinctly inferior to the CloudFront implementation, the base URL for the files is http://cdn.cloudfiles.mosso.com/some-hash-value/yourfile, vs. the more elegant CloudFront http://some-hash-value.cloudfront.net/yourfile. You can CNAME the latter to some nicely in-your-domain host (images.yourcompany.com, let’s say), and in fact, if you’ve used another CDN or have simply been smart and delivered static content off its own hostname, you’d already have that set up. The Mosso method means that you’ve got to go through all your content and munge your URLs to point to the CDN.

Aside from being annoying, it makes the elegant fallback, less elegant. Having the CNAME means that if some reason CloudFront goes belly-up, I can trivially repoint the CNAME to my own server (and I can easily automate this task, monitoring CloudFront deliverability and swapping the DNS if it dies). I can’t do that as easily with Mosso (although I can CNAME cdn.cloudfiles.mosso.com to something in my domain, and set up a directory structure that uses the hash, or use a URL rewriting rule, and still get the same effect, so it is merely more awkward, not impossible).

That might be in part a way for Limelight to differentiate this from its normal CDN offering, which has the modern and elegant deployment mechanism of: simply point your website hostname at Limelight and Limelight will do the rest. In that scheme, Limelight automatically figures out what to cache, and does the right thing. That seems unlikely, though. I hope the current scheme is just temporary until they get a CloudFront-like DNS-based implementation done.

I’ll have more to say once I’ve accumulated some log data, and add SimpleCDN into the mix.

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1 Comment »

Category: Infrastructure     Tags: , ,

1 response so far ↓

  • 1 Mike   November 20, 2009 at 12:36 pm

    Lydia-

    Thank you for posting this information. We have been evaluating a short list of hosting providers and content delivery networks and are leaning towards the Rackspace Limelight solution. This post confirms our internal opinion about choosing Rackspace to host our site in addition to hundreds of our customers’ sites. We will definitely benefit from your advice to use cnames as well. Thanks!