{"id":96,"date":"2005-10-03T15:59:10","date_gmt":"2005-10-03T05:59:10","guid":{"rendered":"http:\/\/www.somethinkodd.com\/oddthinking\/?p=96"},"modified":"2005-11-19T10:01:28","modified_gmt":"2005-11-19T00:01:28","slug":"availability-versus-reliability-versus-ignorability","status":"publish","type":"post","link":"https:\/\/www.somethinkodd.com\/oddthinking\/2005\/10\/03\/availability-versus-reliability-versus-ignorability\/","title":{"rendered":"Availability versus Reliability versus Ignorability"},"content":{"rendered":"

<\/p>\n

Many years ago, I was testing and debugging some software for a set of machines on a rack. The system was designed to have high availability<\/a> – the four nodes were in constant communication across eight cables, mirroring their databases and transparently recovering if there was a failure in the system. During my testing and debugging, each component had low reliability<\/a> – some part of the system crashed or otherwise required rebooting frequently – the MTBF<\/a> for each component was about 2 hours.<\/p>\n

I was pleasantly surprised one day to notice that the system had been up for a whole week! No single node had lasted more than a half-day, but the system<\/em> had been robust in the face of that. Woohoo!<\/p>\n

I was reminded of this experience this week – without the pleasant surprise – as my PC repeatedly froze up at random intervals during extended, intensive data recovery<\/a> operations. It froze up about 15 times – once it survived 8 hours before locking up, once it lasted 33 seconds. <\/p>\n

The difference between this experience and the last one was that there was no synchronisation with other machines and no recovery points. Every time it froze, I lost everything since my last (manual) save. As a result, I couldn’t just walk away and ignore the computer while the data recovery software running – I had to come back every half-hour and interrupt it to save the progress that had been made.<\/p>\n

Sigh.<\/p>\n","protected":false},"excerpt":{"rendered":"

What are the consequences of low-reliability components?<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_s2mail":"","footnotes":""},"categories":[23,24,31],"tags":[],"class_list":["post-96","post","type-post","status-publish","format-standard","hentry","category-based-on-a-true-story","category-cathartic-rant","category-geek"],"_links":{"self":[{"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/posts\/96","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/comments?post=96"}],"version-history":[{"count":0,"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/posts\/96\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/media?parent=96"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/categories?post=96"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/tags?post=96"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}