{"id":1761,"date":"2010-01-15T08:36:46","date_gmt":"2010-01-14T22:36:46","guid":{"rendered":"http:\/\/nsrd.info\/blog\/?p=1761"},"modified":"2018-12-11T19:11:11","modified_gmt":"2018-12-11T09:11:11","slug":"the-law-of-least-astonishment-and-backups","status":"publish","type":"post","link":"https:\/\/nsrd.info\/blog\/2010\/01\/15\/the-law-of-least-astonishment-and-backups\/","title":{"rendered":"The law of least astonishment and backups"},"content":{"rendered":"

A recent twitter posting by Matt over at Standalone Sysadmin<\/a> reminded by of the law of least astonishment<\/a>.<\/p>\n

If you’re not familiar with this law\/principle, and you work in IT (not to mention backup!), you should be. Over at Wikipedia, it’s defined thusly:<\/p>\n

[W]hen two elements of an interface conflict, or are ambiguous, the behaviour should be that which will least surprise the human user or programmer at the time the conflict arises.<\/p><\/blockquote>\n

I can’t stress just how important it is that this rule is applied, both to general IT architecture, and to backups as a specific instance.<\/p>\n

This is why, for instance, I recently covered the idea that if you can’t diagram your backup environment on the back of a napkin<\/a>, it’s too complex.<\/p>\n

The more arbitrarily complex a system is, the more chance there is of misunderstanding what it does. In data protection in particular, misunderstandings can lead to data loss. Thus, arbitrarily introducing complexity at the cost of comprehension is a very, very bad idea.<\/p>\n

Take for instance, you’ve got a script that would arbitrarily remove all indices for backups older than 3 months old. No, I don’t know why you’d have such a script, but I want to use it as an example regardless. You don’t normally run this, but in an emergency if a fileserver does a absolutely huge backup with millions upon millions of files day after day, you may periodically find yourself in the situation of needing to scrub old index data to reclaim space. (Obviously, there should be more space allocated to indices. I’m using this as an example, remember…)<\/p>\n

You might think that for such a simple script, there’s no “law of least astonishment” to follow, but trust me, there is, and in this case, it’s all in the name.<\/p>\n

Consider a few potential names for such a script:<\/p>\n