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From aaron morton <aa...@thelastpickle.com>
Subject Re: Write Performance
Date Thu, 19 Apr 2012 20:37:04 GMT
You should be able to get more than that. 

Run nodetool cfstats, look at the Write Latency (this is the recent latency, i.e. is reset
each time you run it). This will give you an idea of how long an individual node is spending
on a write. 

Fire up JConsole, go to the StorageProxy MBean and look at the latency numbers there. This
is how long the node takes to process a request for a client, it includes all network operations.

How many mutations are you sending in one batch ? You can get improvements by sending more,
up to a point. 

Are you using a single client thread / process ? Multiple clients is better. 

Hope that helps. 


-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 20/04/2012, at 3:24 AM, Trevor Francis wrote:

> Would there be any reason why I can't write more than 875 writes/sec to a cluster of
2 cassandra boxes? They are quad core machines with 8gb of ram running raid 10, so not huge
servers….but certainly enough to handle a much larger load than that. 
> 
> We are feeding data into it through a Flume sink. The disk io remains nearly nil along
with load average across the cluster, but writes peak there. The data being written in is
small (150-bytes). VNstat reveals ethernet bandwidth not exceeding 2mb/sec.
> 
> Not sure if this is a cassandra issue or a flume issue.
> 
> Thoughts?
> 
> 
> Trevor Francis
> 
> 


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