Some basics on (High) Availability in CMS

RE: Some basics on (High) Availability in CMS

Sayantan Basu — Fri, 16 Jun 2017 16:21:42 GMT

Nice One [mention:fdc046d089a04ababb7785fe625c140a:e9ed411860ed4f2ba0265705b8793d05] :)

RE: Some basics on (High) Availability in CMS

Hao Peng — Fri, 16 Jun 2017 15:13:19 GMT

Thank you Alvin and Mark for reading and liking.

@Mark, thanks for your comment. There are indeed things that are not exact science and/or have assumptions that would make the post boring. in this post. 36.8% indeed assumes the components being used are mature enough to have those random failures but stable failure rates.

You raised a good point of those random different points of failure where their reliability is unpredictable. The system and the calculation definitely will be impacted by these areas. These are factors to discuss when a client indeed requires "HA", instead of only focusing on those mature and well known components. However the reliability probability formula do give indications of the "ceiling", which would be a useful thing for setting a more realistic expectation.

RE: Some basics on (High) Availability in CMS

Mark Saunders — Fri, 16 Jun 2017 10:08:47 GMT

Great post and very informative.

The one question I would have is how reliable the figures would be given the the failure rate is not likely to be constamt (this comes from my time in engineering where we would only use the Mean Time To Failure - which is what I think you're suggesting with the 36.8% - where the rate of deprecation was constant).

In our complex IT environments with many different points of failure - many outside the control of the distinct areas such as Content Manager, Application, Publishing (as a service).

Even with that said - I can't suggest a better alternative distribution analysis but wondered if the 'randomness' of other systems impact our reliance on these figures?

RE: Some basics on (High) Availability in CMS

Alvin Reyes — Thu, 15 Jun 2017 17:20:42 GMT

Nice post and excellent context, Hao. The distinction between the application(s), publishing, and content manager is definitely important. Since they're separate in SDL Web, they can be managed at the appropriate level and having the CMS down, for example, won't impact the running website.