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From "Edward Capriolo (Updated) (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-3640) Dynamic Snitch does not compute scores if no direct reads hit the node.
Date Thu, 15 Dec 2011 19:22:30 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-3640?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Edward Capriolo updated CASSANDRA-3640:
---------------------------------------

    Description: 
We can into an interesting situation. We added 2 nodes to our cluster. Strangely these nodes
were performing worse then other nodes. They had more IOwait for example. The impact was not
major but it was noticeable. Later I determined that these Cassandra node were not in our
client's list of nodes and our clients do not auto discover. I confirmed that the hosts did
not have any scores inside it's dynamic snitch.

It is counter intuitive that a node receiving less or no direct user requests would perform
worse then others. I am not sure of the dynamic that caused this. 

I understand that DSnitch is supposed to have it's own view of the world, maybe it could share
information with neighbours. Again this is more of a client configuration issue then a direct
Cassandra issue, but I found it interesting.

  was:
We can into an interesting situation. We added 2 nodes to our cluster. Strangely this node
performed worse then other nodes. It had more IOwait for example. The impact was not major
but it was noticeable. Later I determined that this Cassandra node was not in our client's
list of nodes and our clients do not auto discover. I confirmed that the host did not have
any scores inside it's dynamic snitch.

It is counter intuitive that a node receiving less or no direct user requests would perform
worse then others. I am not sure of the dynamic that caused this. 

I understand that DSnitch is supposed to have it's own view of the world, maybe it could share
information with neighbours. Again this is more of a client configuration issue then a direct
Cassandra issue, but I found it quite interesting.

    
> Dynamic Snitch does not compute scores if no direct reads hit the node.
> -----------------------------------------------------------------------
>
>                 Key: CASSANDRA-3640
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3640
>             Project: Cassandra
>          Issue Type: Improvement
>    Affects Versions: 0.8.7
>            Reporter: Edward Capriolo
>            Priority: Minor
>
> We can into an interesting situation. We added 2 nodes to our cluster. Strangely these
nodes were performing worse then other nodes. They had more IOwait for example. The impact
was not major but it was noticeable. Later I determined that these Cassandra node were not
in our client's list of nodes and our clients do not auto discover. I confirmed that the hosts
did not have any scores inside it's dynamic snitch.
> It is counter intuitive that a node receiving less or no direct user requests would perform
worse then others. I am not sure of the dynamic that caused this. 
> I understand that DSnitch is supposed to have it's own view of the world, maybe it could
share information with neighbours. Again this is more of a client configuration issue then
a direct Cassandra issue, but I found it interesting.

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