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vpanarin84_192084 avatar image
vpanarin84_192084 asked Erick Ramirez answered

Does nodetool streamthroughput affect the performance of read requests?

Hi!

Looking into Cassandra configuration options I see `nodetool setstreamthroughput` which is explained as "Sets the throughput capacity in megabits per second (Mb/s) for outbound streaming in the system".

I'm not sure what means "outbound streaming in the system". Does it affect the performance of query result output from Cassandra node? When this setting needs to be changed?

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Erick Ramirez answered

Operations such as bootstrapping and repairs stream parts of SSTables between nodes. Setting the streaming throughput on nodes determines how fast data is streamed by the node to other nodes in the cluster.

A high streaming throughput will have significantly higher IO and will affect other operations on the node including read requests because these operations ultimately are competing for the same IO bandwidth of the disk and network.

If you are adding a node and want it to bootstrap quicker, you would increase the streaming throughput of the other nodes in the cluster but understand that there is a finite amount of resources (CPU, RAM, disk IO, network bandwidth) on each node and you are allocating more resources to one operation (streaming) at the expense of another (read requests).

Only you can determine how much throughput to allocate based on trial and error. Cheers!

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