MySQL Cluster Pop Quiz

Posted in: MySQL, Technical Track

If you have a 12-server MySQL Cluster with:

1 Management Node
3 SQL Nodes
2 Data Node Groups, 4 Data Nodes per group

And 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.

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6 Comments. Leave new

Matthew Montgomery
March 15, 2008 3:43 pm

Slightly less than 2GB of usable DataMemory+IndexMemory

All nodes in a node group will be identical replicas. So each node group will only hold 1GB. Your usable memory is limited by the number of node groups you have. You will also use some memory for operation records and log buffers (MaxNoOfConcurrentOperations, RedoBuffer, UndoDataBuffer, etc…)

p.s. 4 nodes per node group is not so thoroughly tested and just plain silly.

[[Matthew — you’re right! BTW, I only used 4 nodes per node group so I could have a 2,3,4 pattern — easier to understand if it’s something multiplied or divided by 2, 3 or 4 then it relates to that. I could have said 4 node groups with 2 nodes in each group instead.]]

Artem Russakovskii
March 16, 2008 1:14 am

2GB? Each node group would have 1GB of memory since they share the same data and there’s 2 of them?

[[Artem — you are correct!]]


4GB. Data is stored in data nodes (8 nodes total). Each node has 1/2 of memory dedicated to live dataset and the other half to redundant dataset.


Matic — nope, that’s not it. See the other 2 comments before yours for the correct answer, and why.

Artem Russakovskii
March 19, 2008 7:16 pm

Hehe, it looks as if I just copied the answer above mine, but in reality it’s because none of the comments were visible at the time :-]

Log Buffer #89: a Carnival of the Vanities for DBAs
March 21, 2008 11:55 am

[…] the MySQL world, Sheeri Cabral challenges anyone who thinks they know MySQL to a pop-quiz. She asks, “If you have a 12-server MySQL Cluster with: 1 Management Node, 3 SQL Nodes, 2 […]


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