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The operative word here is "theoretically". Theoretically the concept of CDN's (a broad term to describe the main aspect of Cloudflare's service) gives you gre

by jyap 14y ago

The operative word here is "theoretically". Theoretically the concept of CDN's (a broad term to describe the main aspect of Cloudflare's service) gives you greater replication and redundancy of data. Now this all depends on their overall design (not all CDN's are created equal). You can eliminate SPOF's through replication and redundancy. It's like saying I have 2 cars I can use to get to work. Then you say "But what if both break down?" Uh, 2 cars breaking down is not considered a single point of failure. Take the example of serving a single image on the internet. It starts with DNS. You can have multiple DNS servers for your domain (no SPOF for DNS lookups). You have multiple web servers in different countries. Your web servers point to CDNs to serve the image. Your CDN has multiple DNS servers for their domain. They have multiple servers in different countries to serve up your image. Tell me where the 100% uptime of the single image fails in that scenario. To answer your original question, if Value derived (can be high say for a news site) > Risk involved (can be low depending on provider), then that is when the benefits outweigh the downsides. In most cases, a CDN is meant to give you better uptime as well as provide you benefits such as geographically delivered content and the ability to serve your content to more people (eg. videos and other large media content).

Udo 14y ago
Then you say "But what if both break down?" Uh, 2 cars breaking down is not considered a single point of failure. I'm afraid you might have spectacularly misunderstood my point. The way Cloudflare operates is more closely related to a scenario where either one of the two cars failing brings down the site: that would be either the webserver or the CF infrastructure. Mathematically, the combined downtime of both must be greater than that of either one alone. Tell me where the 100% uptime of the single image fails in that scenario. There is no question that a CDN is generally designed to add robustness and speed to content delivery. But as you said, not all CDNs are created equal. I say this as a (satisfied) Cloudflare user myself: In its default configuration, a basic Cloudflare plan has (almost) no settings. It's not like you make a choice e.g. to host only images there. Using the standard CF plan comes with basically two states your site can be in: either CF is on or it's off. When it's on, the entire traffic of that site is going through Cloudflare, they become your site's front-facing servers. There are some huge advantages to this, for example they block a lot of malicious traffic that way. Coming back to your image example: individual components of the service may be designed for redundancy, but there is still a lot of stuff that can (and does) go wrong with global repercussions, if only for the simple reason that the CDN service as a whole must be centrally controlled. If your webserver is up but CF is down, your site is down. If CF is up but your webserver is down, your site is down (actually it becomes a mirror of some static content for a few minutes before it goes offline completely). This is what I meant by each one of those services being a single point of failure, there is really no way of getting around that fact. I remember the same discussion about CDN-hosted JavaScript libraries. People argued that linking to a 3rd-party server made their site more robust simply because CDNs normally have a higher uptime than a standard web hosting server. This was of course completely beside the point, because (again) either one of the two failing meant the site would break. That's why it has become customary to have a local fallback for CDN-hosted JS libraries now.
- jyap 14y ago
  Your original argument was based on "a service like Cloudflare". I was discussing services like Cloudflare, not Cloudflare specifically. My point is, a properly designed CDN (most common ones) should not cause a wide spread outage to their service where 80+% is down.
- larrys 14y ago
  "In its default configuration, a basic Cloudflare plan has (almost) no settings. It's not like you make a choice e.g. to host only images there. " Correct but you could use a completely separate domain for all the images and only enable cloudflare for that domains. (Not a cloudflare customer I'm just pointing this strategy out.)

by jyap 14y ago

Udo 14y ago

Then you say "But what if both break down?" Uh, 2 cars breaking down is not considered a single point of failure. I'm afraid you might have spectacularly misunderstood my point. The way Cloudflare operates is more closely related to a scenario where either one of the two cars failing brings down the site: that would be either the webserver or the CF infrastructure. Mathematically, the combined downtime of both must be greater than that of either one alone. Tell me where the 100% uptime of the single image fails in that scenario. There is no question that a CDN is generally designed to add robustness and speed to content delivery. But as you said, not all CDNs are created equal. I say this as a (satisfied) Cloudflare user myself: In its default configuration, a basic Cloudflare plan has (almost) no settings. It's not like you make a choice e.g. to host only images there. Using the standard CF plan comes with basically two states your site can be in: either CF is on or it's off. When it's on, the entire traffic of that site is going through Cloudflare, they become your site's front-facing servers. There are some huge advantages to this, for example they block a lot of malicious traffic that way. Coming back to your image example: individual components of the service may be designed for redundancy, but there is still a lot of stuff that can (and does) go wrong with global repercussions, if only for the simple reason that the CDN service as a whole must be centrally controlled. If your webserver is up but CF is down, your site is down. If CF is up but your webserver is down, your site is down (actually it becomes a mirror of some static content for a few minutes before it goes offline completely). This is what I meant by each one of those services being a single point of failure, there is really no way of getting around that fact. I remember the same discussion about CDN-hosted JavaScript libraries. People argued that linking to a 3rd-party server made their site more robust simply because CDNs normally have a higher uptime than a standard web hosting server. This was of course completely beside the point, because (again) either one of the two failing meant the site would break. That's why it has become customary to have a local fallback for CDN-hosted JS libraries now.

jyap 14y ago
Your original argument was based on "a service like Cloudflare". I was discussing services like Cloudflare, not Cloudflare specifically. My point is, a properly designed CDN (most common ones) should not cause a wide spread outage to their service where 80+% is down.
larrys 14y ago
"In its default configuration, a basic Cloudflare plan has (almost) no settings. It's not like you make a choice e.g. to host only images there. " Correct but you could use a completely separate domain for all the images and only enable cloudflare for that domains. (Not a cloudflare customer I'm just pointing this strategy out.)