I have a 3 node Cassandra cluster which I set up a year ago and it is getting quite slow now. It is much cheaper for me to scale vertically than it would be to scale horizontally ( I received free RAM and new gigabit nic cards which I want to put into my nodes). I need the cluster to remain up while I upgrade, but I can't find any documentation on how to scale vertically with no downtime. What is the standard procedure to scale a Cassandra cluster vertically? As well, do all the machines need to be identical (same amount of ram, same harddrive space, etc)?
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What is the standard procedure to scale a Cassandra cluster vertically?
There is not. Cassandra was designed to scale horizontally, although you can try to scale it vertically. Simply upgrade one node by one.
- Read about hinted handoff - the mechanism which will be used when one of your nodes will be down
- Make sure your clients use proper ConsistencyLevel (as hinted handoff isn't counted for consistency level)
- Read what happens after node comes back online
As well, do all the machines need to be identical (same amount of ram, same harddrive space, etc)?
No, but you will have to do load balancing manually. If you will have 4 'old' nodes and one 'upgraded' node, and load will be the same on them (the same number of writes/reads because of token assigment), obviously 'old' nodes will have higher percent of theirs resource usage.
piotrwest
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