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Mysql sharding at our company - Part4 (Cell architecture)

Interesting to know how different people can come to same architecture to solve scalability issues.  I just read this article published today called as cell architecture http://highscalability.com/blog/2012/5/9/cell-architectures.html  and I came up with same architecture in our company as highlighted in the  diagram below and I am calling it as "Cluster" instead of "cell" or "pod" but the concept is same.

You can read a bit more on the link I published above but the main reason why we chose this architecture were:

  1. Failure of a cell doesn't cause the entire DC to go down.
  2. We can update one cell and watch out for a week before pushing the release to all cells.
  3. We can have difference capacity for different cells (Enterprise customers vs trial customers).
  4. We can add more cells or mores mysql host to once cell if it has a capacity problem in one component.
  5. Ideally you want to make it as homogeneous as possible but let say for some reason in one cell people are doing more add/delete files than just adds and delete causes index fragmentation so you can do aggressive index defrag on one cell than others.
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