{"id":5401,"date":"2018-11-14T11:14:53","date_gmt":"2018-11-14T11:14:53","guid":{"rendered":"https:\/\/dbtut.com\/?p=5401"},"modified":"2018-12-06T08:37:07","modified_gmt":"2018-12-06T08:37:07","slug":"high-availability-part-ii","status":"publish","type":"post","link":"https:\/\/dbtut.com\/index.php\/2018\/11\/14\/high-availability-part-ii\/","title":{"rendered":"High Availability Part II"},"content":{"rendered":"

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You should read the first part of this article before reading this article. “High Availability Part I<\/a>”<\/p>\n

The expectation that a system will operate continuously for a significant span of time with minimal downtime is the goal of every organization. For example, with 8,760 hours in a year, 99% availability signals over 7 hours of downtime a month and 88 hours of downtime over the course of that year. In turn, 99.9% availability\u2014\u201cthree nines\u201d\u2014adds up to over eight hours of unplanned downtime, while 99.99% (four nines) translates into under an hour.<\/p>\n

How Many Nines Do You<\/em> Need?<\/strong><\/p>\n

That is the question to ask. The answer will depend on your requirements. While some organizations set their sights on 100% availability, most systems don\u2019t need to hit such heights. Nuclear reactors, missile defense systems, stock exchanges, transportation systems, automated teller machines have a high cost of failure and need high reliability, but web applications may not need as much.<\/p>\n

Smaller businesses don\u2019t need to invest in high levels of fault tolerance, which can require immense hardware and engineering resources. Every time you add a nine, costs rise exponentially.<\/p>\n

Although going for high availability solution is alright, it comes at a big cost too. You must ask yourself if you think the decision is justified from the point of view of finance.<\/p>\n

Two important questions:<\/strong><\/p>\n