Had an interesting situation come up today with a client. We had a situation where a server crashed because it ran out of memory. The calculation we used to monitor memory usage did not take into account all factors. When looking at this, I noticed a couple of things:\tThere are numerous calculations available online.\tIt seems that none of them take everything in account.Wouldn't it be nice if there was a total possible memory consumption status value? It can be a valuable piece of information. (And while I am requesting things, what about peak memory usage by the mysqld server since it has been online?) Realistically, there is almost no case where you would actually use the maximum amount of memory. But knowing how much memory that MySQL server could possibly use would be a very useful bit of information to know.Second, why isn't there an "official" formula that actually shows everything? It's easy to forget things.  []

If you have a 12-server MySQL Cluster with:1 Management Node3 SQL Nodes2 Data Node Groups, 4 Data Nodes per groupAnd each machine is configured to allocate 1G of memory for its function, how much data (data + indexes) can you store in total in your cluster?You can guess, but you get bonus points if you explain why and the explanation is correct.

This is an issue that keeps rearing its ugly head over and over again, and since it greatly affects performance, it is most important that DBAs of any DMBS running on Linux come to grips with it. So I decided to do some research and try different settings on my notebook. Here are my findings.What can you find on the web?A Wikipedia search for the word swappiness will come up empty (any volunteers out there want to write an article?). A Google search will show some pretty old material---the best article I found is from 2004: Linux: Tuning Swappiness. This article includes a detailed discussion with some interesting remarks by Andrew Morton, a Linux kernel maintainer.So, what is swappiness?

Debugging/monitoring MySQL by reading the process memory

MySQL memory handling and memory handling in Falcon